How much Grade work?  Remember that a loader doesn't have any way to adjust the tilt of the bucket to the tracks, it takes a lot of experience to really be able to level with one.  For terrace work and general dirt pushing, dozer any day.  For tree pushing and general farm work a loader is good.  You can tilt the teeth on a loader and do some root raking with it, too.  We bought a dozer about a year ago.  For the amount of dirt work we wanted to do, vs tree work, it seemed like the better choice.  IMHO buy a dozer, and if you have a lot of big trees to take out hire an excavator to come in and push them over and you pile.