I've actuary done field dressing with both methods of field dressing although the gambrel method was done at a buddy's garage near the hunt. Both have pro's and con's but I found it much easier to field dress on the ground in the field. It cools the animal down quicker, doesn't make a mess in the garage and is less weight to lift into the truck.

If you liked your buddy's method a lot, you could always video the next one and have him explain it in detail as he goes.