Earlier this month, we visted Universal and SeaWorld. We stayed 1 night at RPR, 4 nights at HRH, and then switched to the Hilton Garden Inn SeaWorld for our last 2 nights and visited SeaWorld for two days.
I can't remember what stopped us from staying at the Renaissance - either it was full or they didn't allow 5 people in a standard room. The Hilton Garden Inn was fine, although I thought it was pricey ($184). (We paid $159 at RPR and $129 for obstructed view at HRH). But, like you, we like being near the park we are visiting. We had a King Bed, sleeper sofa, micro, mini fridge, coffee maker. It was nothing special, but was certainy adequate. Great bedding. Small pool, but it wasn't at all crowded when we used it on our last day (Saturday). The hotel is within walking distance of SeaWorld. You cross a very low-traffic side street towards the Renaissance (the sidewalks are on the Renaissance side) and then another more trafficked street (4 lanes with a median - no street light) to get to the SeaWorld parking lot.
Basically, the walk from the Renaissance and Hilton are like walking from one of the furthest spaces in the SeaWorld parking lot. The Hilton runs shuttles (not many trips, and not worth the wait) and I would imagine the Renaissance does also.
Personally, I would do a split stay. It would be a shame to give up FOTL access by not staying on-site when visiting Universal.