Satch, I think you should have an "all of the above" choice.
For example... if money wasnt an issue, i would always opt use human grade gear, excpet in the two scerarios mentioned above, exotic steroids, and higher dose gear. When these two arent needed, its always human grade for me.
I believe that you can do great with UG labs as well though, and am not against using them. I would personally rather use a reputable UG lab over Mexi-Gear. There are really much more that you can have with UG gear than human gear, the only thing I can think of to dis human grade gear is the risk of fakes, as NS mentioned, but there are much more risks with UG gear. Sterility issues, powder purity, dosing problems due to filtering or other issues, getting the correct compounds etc.
Needsize, there are also fakes of UG labs out there. Look at how many times BD has been fakes.
I say a safe rule of thumb is to try to cough up a little extra coing, and opt for human grade when you have the choice from a reputable source .. ECXEPT for the above mentioned scenarios. Then try to go with a reputable UG lab, that has proven itself with multiple lab tests, or who has been around for a long time (except IP, hahahaha).
Mavy