Okay, got my ZT 0350 in yesterday, and have been EDC'ing it all day. I'll be honest, so far I don't think it's going to kick either the Ritter Grip or the Stag Arms Manix 2 out of my pocket. There's a lot to recommend it, but also a few things I don't like. Here's a few of my impressions:
Lockup is solid as a rock. The Griptilian can be a bit finicky with blade play, especially if you want to be able to use the Axis lock to wrist flick it out without using the thumbstuds, while the Manix 2 is also rock solid. It deploys quickly and easily using the flipper, but the thumbstuds are basically useless. It's actually rather painful to attempt to deploy using the thumbstuds, since the speedsafe mechanism seems to hold it in until it reaches a certain point. It's the only assisted knife in the list, by the way.
Mine came nice and sharp, and it cuts just as well as any of the other two, although both of the others have been reprofiled to 30 degrees, and the 0350 is a 18-20 degree bevel on each side (closer to a 40).
Personally, I really like the wide blades on all three--makes a much bigger hole when you're stabbing something, and I just feel better about durability if it's a bit wider.
I was actually kinda surprised about how thin (relatively speaking) the blade was. It's no 300 or 200, that's for sure. The Manix 2 and Ritter Grip have comparable widths. That being said, they're all incredibly solid knives. I only have the 0350 on me right now, or I'd put up some comparison pics.
Ergonomics is quite good, although of the three, I find the Manix 2 to be the most comfortable; the handle is designed for a variety of grips, and it has a choil built into the top of the blade and handle to allow you to do more precise work. I think I'll probably like the Ritter Grip as much or more once I get some Kevin Wilkins grips for it, but the stock Noryl GTX handle isn't the most comfortable, and it's probably the least comfortable of the three if you want to choke up on the blade. The 0350 has a thumb detent designed into the blade, so it's fairly comfortable to choke up on. The aggressive jimping on the back of the handle makes for a secure place to put your hand, and as advertised, it's pretty comfortable in a gloved hand (although all three are). I am not sure what the jimping on the bottom of the handle is for, however. Maybe someone else can illuminate us?
The G10 is nice and grippy, although it's pretty comparable to the Manix 2 G10. The handle for some reason looks a bit long, but feels a bit short in a fencing grip, where the other two fill my hand a bit more completely. It think it's just the way the handle curves forward.
Okay, so here's where I stand: If you're going to choose between the regular Manix 2 or Para 2, regular Griptilian, and the ZT 0350, I'd probably run with the 0350. If you're going to choose between the Ritter Griptilian, a Sprint Run Manix 2 (Stag Arms is the one I have, and it's probably the least expensive Sprint Manix 2 in FFG S30V out there), and the 0350, you've got a tougher decision.
They're all around $120 knives, although the Ritter Grip may eventually cost you more, because you may want to buy custom grips for it. Just based on that, I'd probably go with the Manix 2 or the ZT 0350, with the edge going to the Manix 2 Sprint because the useless thumb studs on the 0350 kind of bother me, and I prefer the handle design on the Manix 2 to the handle of the 0350, and the FFG blade geometry cuts a little bit better than the high flat grind on the ZT or the Ritter Grip. Now, that's just my preference. Any of the knives I've mentioned will be comparable in price, quality, and performance. It's just the little details. They're all among the best EDC knives for under 150 dollars, and I wouldn't hesitate to trust my life to any of them.
As for the sharpening question--I STRONGLY recommend getting the Sharpmaker. It's very easy, and much cheaper than an Edgepro or Wicked Edge system, and will get knives much sharper than freehand if you're not super precise with freehand. I had much the same problem as you, and went with the Sharpmaker after considering many recommendations, in part because it is so much less expensive. I don't regret that choice in the slightest; it was worth every penny (and I paid full price to buy it from the Spyderco Factory Outlet). If you're looking for a shaving edge, you may want to also invest in the Ultra Fine rods, and if you feel like you may need to do some reprofiling, I'd really recommend the Diamond rods. Plus, you can sharpen serrated blades with it as well.
Just my two cents. There are many other members on here with more experience and knowledge than me, but I feel confident you would be very happy with any of the three knives I've mentioned, and with the Sharpmaker as well.
Just be aware--you're almost certainly going to get to the point where 100-200 dollars for a knife feels like a good price, and you'll be hesitant to spend 400+ on a Sebenza, Strider, Darrel Ralph, or a custom, or something else comparable. (That's where I'm at). Then you may get to the point where you won't settle for anything less than one of those. This place is horribly addictive, and very bad for your pocket book. Best to get used to it quickly.
