Allow me to ask a preliminary question: when are you going to WDW? My experience has been that the FDP isn't necessary to insure a seat at Fantasmic unless you're going at an extremely busy time of the year like Christmas.
The last 2 times we went were in early August, a time when crowds aren't "peak" but the parks are still pretty busy. We've done the FDP both times to insure we had seats for Fantasmic, but found each time that seats were available as late as 10-15 minutes before showtime. Next time we'll probably just have dinner at one of the Epcot/MGM resorts and then go to Fantasmic from there.
(BTW, to answer your question, we've done H&V for our FDP both times and enjoyed it both times. However, there's a pretty sharp split of opinion on H&V for dinner. You can search this forum and read pretty diverse opinions on it. My review of our August H&V experience is
here.)