Last summer we went for 7 nights in a King Suite at RPR and LOVED it. It was the first time we had ever gone for more than 3 nights and now I don't want to go unless I can go for at LEAST 5 nights.
Like everybody is staying, Universal is a MUCH more relaxing experience than Disney. With your Express Pass access as a hotel guest, you will be able to have both parks done in two days. So, instead of rushing to hit every ride in the first two days, you can visit the parks in the morning, come back to the hotel for an afternoon swim in the great pool, and then head back to the parks in the evening. Or if your like me and love riding rides, you could ride MIB 20 times in a row to try and get a perfect score...but you would have to be crazy to do that

(it was more like 25 times, and I still could not get it...975,540 was the closest I got

)
You also will have the new mini-golf courses on Citywalk which look like they are going to be a ton of fun! Since they have two different courses, you might want to do one on the 2nd night and another on the 4th night to break it up a little. Have a nice dinner at Citywalk after the parks close and then go and play a round of golf.
One thing I suggest not doing is eating at the Island Dining Room at the hotel. Some people seem to enjoy it, but I have always found it to be very expensive and not the best. The Breakfast buffet there is $20 a person and the food is just "ok" for the price and you don't have a huge selection to pick from. I enjoy eating the breakfast crossiant (sp?) at the bakery inside IOA at the end of the main entrance into the park. It is really good and a nice hot, filling breakfast sandwhich for around $6.00. However, eating at Jakes at the hotel is highly recommened! I love eating at Jakes. We ate their nearly everyday on our last trip.