Oh, I've stayed in both, but only wrote a TA review on one.

The Convention Center HI, IIRC, was HUGE. I got a suite, though I don't think it was an upgrade, more like one of the only rooms left. It was big and clean but didn't have a flat screen TV.

The restaurant had good food. Obviously the location isn't bad, but a car is necessary.

I'd stay there again, though I would probably choose the HI Downtown Airport over it with the location that's closer to the Old Market and I assume that its regular rooms are bigger. It's also a new hotel.

I can't really compare the waterparks/pools, sorry though. I do remember thinking that the HI Convention Center pool was pretty big, but also the Downtown waterpark was very cool with the huge bucket that dumped water on people.

Hope this helps.