i would definitely wait on the clown trigger, for the bigger tank, they really should go into at least a 135, beautiful fish, but hey gett up to 20 inches(and you want to plan on him being a 20 incher, even if he is only 5 or 6 when you buy him), and in a 75, this would be able to be your only fish, nayway, especially since the 75 is only 48 inches long, the fish would get to be almost half the length of your tank, for a 75, i would consider a different trigger, unless you ARE buying a larger tank in the next year, or the lion, another draw back to a clown, you can only put so many fish in a 75, and a clown as it matures, would make a snack out of anythign that you could fit in there, because all of your other fish would have to be smaller(much), but dwarf lion, you could have a couple of other fish the same size, just so long as they can't fit into his mouth(they can and probably will eat anything they can fit in)
HTH