Palio for every reason you stated above plus the best Italian food at WDW. It is a favorite restaurant of mine. Be warned though that it will be closing for a renovation sometime in the near future. Contact the restaurant directly to find out when. You can find the number at the swan and dolphins main website under dining. Unfortunately, this restaurant was never busy. It seriously has great food and top notch service. Try it if you can.
BUT, be sure there aren't any huge conventions going on. When we were there, and it was PACKED with huge tables of business professionals. We had to yell across our table of two to be heard. But, the food and service was amazing!
Palio is one of my favorite WDW restaurants. I have never been to Portobellos, but will probably not try as long as I have Palio. The food & service is top-notch.