I've been to all Goodwood events (Members Meeting, FoS and Revival) and have been to Spa for the Six Hour Classic, but not F1, but I have been to Silverstone numerous times for the F1.
For me, Spa is one of the most beautiful and evocative places you could ever go, whether motor racing or not and you could spend a whole weekend exploring the new track, old track and the villages with no motor racing, but if the historic events were on it's awesome, the noise and speed is incredible and I think for current F1 you would probably enjoy, but I'd recommend the classic event in September.
Goodwood FoS is fantastic, but only if you're a massive car/motor racing anorak - you could spend the whole weekend just looking at each of the cars and never actually seeing the much of the action, as there isn't much and I'd actually recommend watching the YouTube live feed all weekend from the comfort of home - I go on the Thursday, see the cars and people I want to and then watch if at home ;)
If you're talking about going to Goodwood for the Members Meeting or the Revival, then great, as a one-off you will love. I enjoy the whole Members Meeting, but the Revival is now a little too commercial, too crowded and I don't enjoy the racing, so again, I pick and choose the races I want to watch from the timetable on their excellent YouTube live feed.
It really depends on you preference, but I can definitely recommend Spa, just make sure you have access to a bicycle to really enjoy it.