If you have the money and space, go with the 75. Its 18" deep, which will be good when your fh grows bigger. The 55 is only 13", which will be a little tight for your fish to turn. I went thru what you are going thru now.
Later on, you will go with show quality and want quality over quantity because you will get tired of taking care of the fish and it seems like its work rather than a hobby.
Later on, you will go with show quality and want quality over quantity because you will get tired of taking care of the fish and it seems like its work rather than a hobby.

<-- You