A few thoughts on the pros and cons of various kinds:
Traditional rounded, red-painted, guardless, wood-handled varieties are classic, comfortable to use, but the red-paint finish is a tad more slippery than I like. This is especially the case when you're drawing it out of the sheath: the traditional sheaths are friction-fit only; the knife is just stuffed into the sheath until the inside of the sheath grips the wide part of the handle. Given this, the natural means of unsheathing the knife is to grab the handle with fewer than all of the fingers of one's hand, holding the sheath in the other hand, and just tugging gently until the friction gives way and the knife comes loose, usually with a minor jerk regardless of how gently and carefully you do it. Yeah, you can kind of develop a technique of working the knife and sheath gently sideways and backwards and forwards, but it's hard to hold the knife with a very firm grip while you're doing all of this. Bottom line: there is a bit of awkwardness and, usually, imperfect grip on a slick handle involved in drawing a traditional Mora from a traditional sheath. I have opted to remove the slick red paint from mine, replacing with a coarser dye-stain-type finish with light linseed oil over it, for greater grip. Also, I have roughed-up the part of the handle that protrudes out of the mouth of the sheath, to improve grip. Not major gripes, these, but worth considering.
Of the traditional Mora knives, the word on the street (or off the road, more appropriately) is that the laminated-blade versions may actually not be as robust as the non-laminated, because these blades are so thin that people report the laminated blades bending relatively easily. I've never had this happen, personally, but have never used a laminated Mora hard enough to make that happen yet.
The old Eriksson models differed from the old Frost models in that the former have a not-quite-full tang that is epoxied into the handle, according to "Ragnar" of Ragweed Forge (the lowest-cost purveyor of Mora knives I've yet found, aside from eBay sellers). "Ragnar" thinks that this actually makes Eriksson knives sturdier than the Frost models, in which the thin tang extends all the way to the butt of the handle, and is secured by a little metal collar wedged into the tang-hole, around the tang. I think the Eriksson models were a bit thicker in the blade, too, than the Frosts. No real opinion on these features, but I pass the info along for your use. (I say "old Eriksson" and "old Frosts" because I understand that the two companies have recently merged, and I don't know what effect this may have had, or may have, on the models now being made.)
Another variety of wood-handled Mora knife you'll see often has a pronounced swelling at the butt end of the handle. This, I think, allows for much better control, and a much-surer grip. Knives with this construction usually come with unpainted handles, and thin cross-guards between the blade and the handle. I have no objections at all to these; they're great, usually little, knives.
Frost's Clipper models are great. They're tough, and the rubber on the handles eliminates the concern about grip that I have with the traditional rounded-wooden-handled Moras. Their handles are great for small-to-mid-sized hands, and I (who have pretty big hands) have no problem with them, either. I use the high-carbon variety. The Clipper sheath retains the knife by part of the handle's snapping into the plastic sheath. I don't have a heck of a lot of confidence in that locking mechanism, and I wonder if it might let a knife get knocked loose in heavy outdoor activity. I have heard of people who've had the Clipper sheath (named for the fact that one doesn't put one's belt through a belt-loop; rather, the sheath has an integral plastic clip that one clips down over the belt) pop off their belts sometimes. This could be fixed by adding some other means of securing sheath to belt--a little cordage would do this trick easily. Ergonomically, I like these knives the best of the Moras I've used.
Frosts Craftsman: These have bulky handles--great for those of us with big hands, a little less than perfectly natural for those like my wife, who have small hands. The smooth plastic handles are, in my opinion, far too smooth out of the box. However, if you take some very coarse sandpaper and sand the handle for about two minutes, you'll find yourself with a handle with a surface that reminds you of rubberized handle material like Kraton. A little fuzzy-looking, maybe, but very grippy, even under water; I'd have no problem cleaning fish with it. (Suggestion: tape the edge before sanding, to avoid cutting yourself while your attention is focused on the handle.)
The sheath-to-knife lockup is, again, done by the knife handle snapping in to the plastic of the sheath. On mine, this snapping-in seemed more secure than with the Frosts Clipper. The sheath is also designed for ambidextrous use, unlike the Clipper, which is designed so as to keep the edge toward the back if one clips the sheath to one's belt on one's right side. One important additional feature of the Craftsman, though, is that it has a large lanyard hole in the butt of the knife. That hole, I have discovered through a little experimentation, is exactly the right size to take a mini-carabiner. The sheath is set up so that there are some wide holes at the top of the belt loop part of the sheath, which you can use to thread the mini-carabiner through after you've put it through the lanyard hole. Result: you can firmly lock the knife into its sheath with a mini-carabiner. If you want speed of draw instead of security of retention, you can always just not run the carabiner through the scabbard, maybe just leaving it through the lanyard-hole of the knife. If I were going to use a Mora as part of a neck-rig like some people advocate (kinda iffy, I've always thought--not sure I want to be in an unpredictable outdoor situation with a noose around my neck, made of cord with a higher test-strength than my neck!

), I'd probably use a Craftsman, with roughed-up handle, with a mini-carabiner locking the knife into the sheath. For what it's worth, the Craftsman sheath is also thinner than, say, the clipper sheath, in the part where the blade is covered. This may make it easier to do things like tape a lighter, ferrocerium "metal match" rod, etc. to that part of the sheath, as Cody Lundin advocates in his famous book
98.6 Degrees. The Craftsman is available in what Frosts calls "triflex", which is high-carbon steel which is differentially tempered so that the edge is hard and the spine relatively softer so as to make the knife less brittle. On mine, even that supposedly-harder edge was rolling a bit under some medium-weight batoning, but this may be due to the problem many encounter with Moras before they're sharpened a few dozen times, that the very edge may be a little less-hard than the steel a little ways into the knife, due, perhaps, to the polishing process heating the edge enough to draw a bit of the temper. Conventional wisdom is that you can cure this by just sharpening enough to get down past the softened steel at the very edge of the edge.
I've never held one of the Mora 2000 knives. I find them interesting, and I imagine that the rubberized mid-portion of the handle will make it about as grippy as the Clipper. I imagine that the swelled butt-end of the handle will make it easier to withdraw from the sheath in a controlled way than the classic rounded-wood-handled Moras. From pictures, it looks like the sheath is vaguely cylindrical in shape, which means it's more bulky down around the blade part than other Mora sheaths. I've read somewhere--probably Cliff Stamp, on Bladeforums--that some people find that the Mora 2000 blade breaks more easily than some people are comfortable with. Given that, I'd be inclined to go with the Clipper, probably in carbon steel, if I wanted a Mora-2000-like knife. Reason: I know the steel on the Clippers is tough, probably a lot tougher than on the Mora 2000; also, on a good day you can get a Clipper for well under $10 on eBay, whereas the going rate for Mora 2000s seems to be around $30.