Looking at the value they are bloody expensive bits of kit.
Obviously the best way to check the pieces is too build them. And to build the various variants in each set.
So built the submarine, No photo, then built the shuttle which was the main one.

Missing a few pieces (inc the wheels, somehow!) So I've ordered the parts needed on Bricklink (great site)
Then built the second set.

Missing 6 pieces so I'm about to order them. Need to build the second version in that set now. Really is a chore

Been looking at the star wars ultimate collectors sets though. They are £1000's of ££££!
But, if you buy the pieces separately it works out quite a bit cheaper. If you buy cleverly. The other thing is to raid car boots. Thinking about it hmm.