The Vision and Savannah are both great bows but are different. The Savannah is shaped, both in grip and profile, more like a standard longbow. Low locator grip. Strung profile that has a fairly continuous curve, not quite D-shaped but not like the Vision.
The Vision is considered to be more of a hybrid in design. It has a long riser, more contoured grip, and a more aggressive D/R profile. Strung it shows its reflex in the tips. It is 4" longer than the Savannah, as well.
Personally, I like the Savannah but I love my Vision. It is smooth, has excellent speed, and it is easy to shoot. I've shot a bunch of longbows and hybrids and my Vision has the best mixture of qualities I want in a bow.
Chris