Upgrading from a 20g to a 55 or 90 need advice/stocking help

[LazyTF1]

which should choose (tank wise) the 55 is 48x12x20 and it has a built in overflow the 90 is 48x18x24 and has an eshopps overflow box both have sumps, skimmer, and return pump. In my current setup i have 2 clowns, one royal gramma, and a watchmen goby pair. I've been in the hobby for nearly two years and really want to upgrade to one of the two tanks so anyone with those tanks i would appreciate any input!

 

[Biokabe]

Don't even entertain the 55. Go to the 90 and don't look back.

I've had a 55 before, and it's really not pleasant. The tank is so narrow that you'll struggle to get a decent aquascape, and you'll always be wanting fish that need that extra space from the larger tank. I was SO much happier once I moved up to my current tank (close to your 90g dimensions).