This whole Sunpass, E-Pass, E-ZPass, Uni, and Pro thing is confusing. Here is what I've been able to find.
E-ZPass is a northeast system. It works in New England and down through Virginia. Florida toll roads have just recently begun accepting E-ZPass but there are reports that it is still not completely working.
E-Pass is the system established by the Central Florida Expressway Authority which is based in Orlando.
Sunpass is the system established by the Florida DoT based in Tallahassee.
The different transponders:
E-ZPass: New England through Virginia. Toll roads in Florida are converting to accept this but may not all be ready yet.
E-Pass: FL, GA, NC
E-Pass Uni (used to be E-Pass-Extra): E-Pass states + E-ZPass states all in one transponder
Sunpass: FL, GA, NC
Sunpass Pro: Sunpass states + E-ZPass states all in one transponder.
Sunpass Pro or E-Pass Uni? They seem to be the same price ($14.95) and cover the same area. They are issued by different Florida Authorities.
Here is a 2019 article which discusses this question.
I have an E-ZPass from my previous residence and purchased a Sunpass here. I will continue using both until I decide to break down and buy a dual transponder. I will probably go with the Sunpass Pro only because I already have a Sunpass account.