Hi Max,

If your plan is to keep it plugged in and on 24/7 (or something close to that), then (in my opinion) the 25A unit is probably more than enough, especially with your solar panels helping some. On the other hand if you're going to be off the grid for extended periods then come back and plug in to recharge, you'll appreciate the larger unit.

By keeping it plugged in, you're never going to run the batteries down at all. You'll essentially be living off of the charger.