The Ontario Machetes come in 12" (camper), 18" (USGI) and 22" (jungle) blade lengths. My fav's are without a doubt the Traditional cutlass 12" Camper, 12" Beavertail and 18" _Plain_ spined USGI. If I had to pick one for all around use it would be the 18" plain spined USGI, but I think most folks interested in a large knife would be better served by the 12" Machetes than most more publicized med, to large "choppers".
The 22" is long enough to be unweildy and hard to carry and is also too flexible to really be good at chopping hardwood. The 12" are joys to carry and use, and get taken places that most times might otherwise indicate a far inferior smaller belt knife. I've tested these things against such disparate items as USMC Kabars and CS Kukri's and various camp hatchets and the ability of the 12" Ontario Camper's machete to chop even hardwood is FAR greater than what most folks might assume. They're not likely to best something like a HI kukri, but they really will beat most cheaper kukri shapes, including CS's plain, lowend one. (Don't know about their better ones.)
In my experience the Blackie Collins "D" handle that's supposed to be an improvement is such a disaster that it totally ruins the concept. That soft plastic knuckle guard, in NO way makes up for the fact that the handles are soft enough that vibrations will loosen the rivets in short order. Nor does it make up for the handle being poorly shaped and highly condusive to simply forming blisters. Get the hard plastic USGI handle and file it to fit the tang. (Most of the ones I've seen/used have slightly oversized handle slabs that need to be better contoured. Done up right, by filing the harder USGI handle and perhaps adding a bit of grip tape, the standard soldier handle is really a pretty decent thing to use for hours and hours, days at a time, clearing brush or mending fence lines.
The "saw" teeth on the back of the spine really aren't good at sawing and simply hang up the drawing of the machete. (If you want to know the truth they weren't originally put their to saw trees in half, but rather to make square lashing notches in poles for projected mil spec survival use.) They've got little function on the tool for regular use. I'd highly advise getting the plain backed ones. (Unless you just like the idea of building a raft out of coconut palms enough not to mind the fact that mostly the teeth are in the way and totally preclude splitting firewood by bashing on the spine.)
The mil spec plastic sheathes are perhaps the best readily available commercial sheathes, despite the "built-in sharpener" being more of a joke than a function. The standard cloth sheathes are absolute junk and are, IMO, unsafe for field carry, since they offer no puncture protection. Making a homemade Kydex sheath for the machete of choice is easy, and is necessary if you fancy a plastic sheath for any config. other than the standard 18" USGI Cutlass shape. (Actually, there may be some USGI plastic sheathes for the 22" but they are lots harder to come by.)
Ontario does the machete so right that it's just a shame that most folks get their first impression of the limitations of a machete from cheap Asian imports that really aren't even all that much less expensive and are vastly different animals when it comes time to actually use them. The amount of cutting that the <$20 Ontario line offers is just amazing.