loaded question for sure!
for me, as my kids are 5 and 7, id pick harbour lake to visit again (and will do so next summer, guaranteed). Thats not to say that river island is bad in any way shape or form, but there are a variety of things that put HL over it if i had to choose!
mostly the reason is that at river island, the pool area is a sprawling metropolis and im not yet comfortable just letting my kids wander off like that. vs harbour lake, it really didnt matter where they went across the entire pool area as you could keep them in sight with ease.
now with THAT said, once my kids are a bit older this will likely flip flop as id be happy to let my kids wander around and enjoy everything on their own (within the confines of the pool area) and i can see older kids (teens) being very bored at harbour lake.
activities at harbour lake also take the win. plenty to do at orange lake too, but its all spread out across all the villages.
id rate the rooms a tie, id have no problem staying in either...though a huge pet peeve at orange lake is the lack of a wall outlet anywhere near the dining nook area! not even one!
so in the end, its really down to what sort of family vacation you have in mind! young kids that you want to see, but not have to hover over all day long and have an unlimited supply of other young kids to play with all day? harbour lake is the answer. once they age out of that, i can absolutely see returning to orange lake for a summer vacation!
will say the arcade at the main village is pretty incredible! kids cant stop talking about it!