I took a 3mm full suit with me to Oahu in July summer before last. Wore it once, then switched back to my 2mm shorty and never put the full suit on again. Temperature was consistently in the high 70s.
I went on a night dive one night with a guide and another couple from Arizona who had just arrived from the mainland earlier that day. While we were waiting on the boat to pick us up, the Arizonans saw me wearing my shorty and changed out of their full suits into shorties.
The clacking sound of their chattering teeth on the boat ride back practically drowned out the boat engine. I felt so sorry for them. They were freezing!
Can't argue comfort.