redearslider.com

I was wondering if it would be better to get a 40 gallon tank that is shorter and not as deep but wider, or a 55 gallon tank that is tall and long. Help with which would be better would be helpful.

Generally, wider is much better. Either will need to be upgraded in the future, so I'd shoot for the cheapest one, unless that 55 gallon is very narrow (less than 12").