I usually try the folders out and let them kind of tell me which they feel better in. Some carry better in the pocket tip down, some tip up, some feel better in the hand and work better one way over another and others it just doesn't matter. On those I always go tip up which is actually the one I prefer.
On the Kabar Dozier Thorn, I couldn't really even get comfortable with the knife and didn't feel it opened as easily in tip up so I put it back to the factory tip down carry even after drilling and threading my own holes to remount a clip on it.
On the BenchMade Dejavoo its hard to justify tip up when it sits nearly invisible like it does in tip down from the factory. Due to the handle shape it would simply not utilize the low rider style pocket clip to its max potential in tip up so to me its not a good move.
Anyway, thats how I do it personally. To me how a knife rides in the pocket is just as important as the blade, the shape, the feel and looks and anything else, especially when you consider that this location on the pocket is where it resides most of the time when its on you.
STR