I live between Tampa and Gainesville, and have lot's of friends in G'ville so I ride Santos, San Felasco, Alafia and Boyette pretty frequently. Without knowing which trails in Santos you ride it is hard to make a suggestion, but you really cant go wrong with any one of them.
<pure opinion> San Felasco is my least favorite of them all because it has no technical terrain. If your favorite trail at Santos is Vortex you will be disappointed. I use SF to test my cardio fitness and just to get in the mileage. It is probably one of the more scenic rides and you will spot lots of deer and other wildlife.
I have stopped riding Alafia as much because Boyette offers a better mix of trails and isnt as crowded. The new Spider Berm is a really fun flowy loop, and the views of the lakes makes for a nice ride. The Abyss and Ridgeline rival anything that Alafia has to offer and the drops on Ridgeline are WAY bigger and flow way better.
just my .02
Unfortunately I will be at Santos this weekend, but if you are riding any other weekend, PM and I'd be happy to guide you around!
-mike