I do not have any experience with the BK7, but I own the BK2 and the BK9 and I have handled the BK10 with aspirations of purchasing one soon.
Though the BK2 and the BK10 are similar in size, length and width wise, they are dramatically different. The BK2 is a veritable beast with a thick, stout blade and a drop point (I think it might be the thickest blade in the Becker lineup). It is pretty much a concrete buster and you can find numerous stress test vids on YouTube demonstrating its many abilities aside from its primary function as a knife. Though it is technically my wife's knife, I have carried and used it on numerous occasions and I have found it to be an excellent knife for just about any camp task. I would say it's primary shortcomings are in regards to its slicing and finer work capabilities. Though I have seen guys treat the edge in a manner to improve such traits, it is still a beastly knife that is more at home processing wood and chopping through elk bones (definitely not much of a skinner), than filleting a trout or dicing up tomatoes...
The BK10, on the other hand, has a much thinner blade with a clip point and swedge. I used to think that the BK10 was useless since the BK2 would clearly outperform it, but I am afraid my experiences in the field have done much to evolve my thought processes regarding this. As a result, I find myself looking at thinner, "slicier" knives and I think the BK10 will prove to outdo the BK2 in the regard.
If you are looking for a brutish tank of a knife that is practically indestructible and can baton through cinder blocks, then the BK2 is your knife.
If you are looking for something a bit more delicate, but no less effective, then the BK10 will fit that role rather nicely.
Plus, if you are bringing your 7 or 9 along with, both of those should do exceptionally well at clearing shrubberies and processing firewood, leaving your smaller knives to do the more delicate tasks such as food prep and the like.