I have the 40's, two of them running in my 180g. had them for a few months and they seem to be working fine with no issues.
I would get the 40's though for a couple reasons:
Only a few bucks more than the 25's
You may upgrade at some point
and- They are adjustable after all. I dont keep mine fully jacked up, I use the else mode and am at about 50% intensity.
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.