It seems to be hit and miss with suppliers. Any supplier that says they have "German" pans is lying - almost all the replacement metal comes from Brazil or Taiwan. The Brazillian pans seem to be a little heavier than most and that's a good thing. For stuff like this I usually use CB Performance, but I've heard that ISP West and aircooled.net have decent stuff.
Other than lower shipping and initial lower cost, no. If you're used to welding thin materials, than certainly only order what you need. I tend to be anal about replacement stuff; if the rest of the pans are even remotely suspect I replace them (or fab my own from angle iron and plate).
Got the floor pans in. Now I need to put the drop section in. The section I had was about a 2" drop. I was thinking of ordering a set from David. He sells a set with a 4" drop. Just wondering how deep everyone else is using. I'm 5'11". I can make my own but after you figure time(welding and Fabrication) and materials the ones David is selling aren't that bad of a price.