Deresa and squamosa are the easiest to injure with debris (sand and whatnot). FYI, clams actually have gills that use oxygen like fish. These gills can get cut and maimed if you have a sandstorm (redecorating your LR and sand :p ).
Teardrop maximas are nice
Squamasos are also nice. I personally like gigas clams, although they can outgrow the tank in a few years
If you do decide to get a crocea or maxima, I'd move a little bit of that sand (good idea to have some) but make sure they can reach the rock. They attatch their byssal threads and hold on for dear life