Totally worth staying on site for both hotels. I got an AP rate for our US hotel stay, as there were no general public discounts for when we were going. The awesome rate for HRH, plus 10% off food and merchandise paid for the AP pass VS regular pass rate.
Stay at HRH if it appeals to you, I took the short cut path from HRH pool to US and made it in 2.5min. This made it so easy to take a break mid day and then come back later for cooler weather and less crowds. HRH has a way different vibe than PBH and our teens were in love with HRH.
The unlimited express pass is a wonderful benefit for onsite guests. We went to WWOHP early and then toured the rest of the parks at our leisure with no real plan. The express lines has minimal to no wait, even when the regular line waits were 120min for the big rides.
When checking into a US hotel, be prepared for your room to not be available until 4PM. I have tried x2 for an earlier check in and neither time it was possible. We just hung out by the pool at HRH and tried to leave WDW as late as possible