E-Pass and SunPass both work on all tolls roads in FL,GA and NC. The difference is E-pass offers discounts on toll roads in central Florida and SunPass does not...we use SunPass
Those discounts are not available to the occasional user. You need to be a daily commuter to reach the threshold where the discounts kick in.
The toll rates, which are discounted from the cash rates, are the same for both.
E-Pass is cheaper to purchase. The first E-pass sticker is free; I don't know about subsequent ones.
SunPass used to have a more user-friendly web site; I don't know whether that's still true. SunPass also has a smart phone app; I don't think E-Pass has one.
There are differences in funding methods. For example, cash can be added to E-Pass at a few designated toll booths, while cash can be added to SunPass at some check-cashing stores (for a fee). There may be other differences, such as minimums, auto-replenish amounts, and refunds.
Both can be ordered on their respective web sites. SunPass can be purchased at many drug & grocery stores in Florida, and at Turnpike service plazas; E-Pass can be obtained in person only at the designated toll booths or at their East Orlando customer service location.