The majority of the lush vegetation is on the Hilo side. There's definitely less resorts. And it rains more, for sure. Yeah, it's a bit older

If you want to stay at a nice resort the entire time, stay in the west side. But there's more than a half a day of stuff to do on the East side so head over there for at least one or 2 day trips with that much time available. Multiple hikes. Multiple waterfalls. 2 different botanical gardens you could go to.