What servos for 1/4 scale?
It really depends on how much you are willing to pay. I'm not into 3D myself, but with the throws necessary you will need good authority. I'm finishing up a Midwest G-202 with Hitec HS-77BB (~$24) on the ailerons and elevator halves and a HS-645MG (~$38) on the rudder. With a 6V battery pack, the HS-77BB will put out 77in-oz and the HS-645MG 133in-oz. Hitec give you the most bang for the buck, although some servos don't center as well as others (most notably the HS-605BB).
If you can afford more, Hitec makes digital versions of their HS-625MG and HG-645MG (HS-5625MG and HS-5645MG respectively). National Hobby sells them for $47...
Hope this helps!