If you must have a lockblade, the 111mm versions are the only way to go. However, the Farmer, as mentioned, has the basic tool loadout that works best in the bush, and has a stronger backspring than the non-locking, red handled SAK's. Also, the awl (for size and position) on the Farmer is the best of the lot; I really like having a good awl on my SAK.
However, if you want a knife that has a good tool loadout that will allow you to improvise with scrounged materials, while not being super bulky, I'd suggest the Ranger. I've tried a number of different SAK's over the years, and decided that the Ranger was the best compromise. It has all the tools of the Farmer, plus a small blade (kept razor sharp for emergency use), and other handy tools like a file and scissors; on the back there's a small screwdriver, plus a small wood chisel that I've used many times. The Ranger is a great knife for most any outdoor use.
However, if you want a knife that has a good tool loadout that will allow you to improvise with scrounged materials, while not being super bulky, I'd suggest the Ranger. I've tried a number of different SAK's over the years, and decided that the Ranger was the best compromise. It has all the tools of the Farmer, plus a small blade (kept razor sharp for emergency use), and other handy tools like a file and scissors; on the back there's a small screwdriver, plus a small wood chisel that I've used many times. The Ranger is a great knife for most any outdoor use.