Hi,
The side to side play on the Okapi's is easy to fix. Just put the hinge in a hard steel surface and rap the hinge rivet with a light hammer. Don't over do this, it's easy to hit it again if you need to. This is the traditional way of adjusting slip joints, and it still works fine. I try to remember to check them before I send them out, but I may have missed some.
As to which is best, as usual it's a series of trade offs. The Okapi come to me very dull, especially in the larger sizes. As mentioned earlier, they are good carbon steel and sharpen easily. I'll put a rough working edge on any I sell for an extra $2. I'd have to say they are less consistent than the Opinel's, but I think they look more interesting (to me), and not everyone wants to fool with the locking ring. They are considerably less expensive than the Opinels, but in this price range that doesn't matter much. You can get either for not much more than the cost of a trip to McDonalds.
The Opinels have excellent blade geometry, and usually better edges. The frictin fit can be a problem. In damp weather the knife can be difficult to open. After much use it can become too loose, and open up in your pocket, which is a hazard. I've cut myself this way. This can be cured by soaking the handle in linseed oil to swell the wood a bit. You don't want to use water for this, because the wood fibers will swell and crush, then will be looser than before when it drys. I've also seen folks drive small tacks in the end of the handle to tighten it up.
I carry both brands (not necessary at the same time), especially when in period attire. Both get modified before I carry them. The Okapi just needs to be sharpened and tightened up if necessary. The Opinel gets the handle reshaped. (See the image) This actually takes a lot longer.
Thanks for all the kind words!
"Ragards,"
Ragnar
http://ragweedforge.com