Well, the trick is simple, when comparing lockbacks to slips:
1. Lockbacks tend to allow brute strength over finesse.
2. Slipjoints require finesse.
The main difference is that you have to cut more, press down less. I've used a mighty thin Queen #11 at work for about a year, and an equally thin Old Timer 8 for the five years before that. It's retired now, as the blade was getting worn down, but I never had a problem with it.
Maximize finesse, minimize force, and you'll do just fine.
If you want a cheap starter, Victorinox is good, as are Schrade and Camillus. Plastic or metal handles, either SS or CS blades depending on the maker. Queen's a step up, with D2 and a pretty decent range of materials, while Case offers about every handle material under the sun. Their SS is pretty shoddy, though.