That depends on what you are going to do next. When you get done with the sailplane you might want to move your gear from this plane into a little sporty electric. In that case you would want the mini servos. If you think you might want to try larger electrics and possibly nitro planes, you are going to need some standard servos.
If you don't know what you want to do next, since you already have some micro servos that will work fine for smaller electrics, and since standard servos are cheaper, get the standard servos.

If you KNOW you are going to move into sporty nitro planes get ball bearing servos like the Futaba S3004 or Hitec HS-325HB