I think the decision was made for me.....by the finished garage slab height final i calculate ceiling height is 11' 10 1/4" so 4 post lift it is....turns out I now have a super slab depth of a minimum of 8" and much more in those strengthening grade beam areas almost like like 20" thick i think the guy doing the gravel and rebar work was down 3" more then he needed to be and when they brought it up to the correct slab height i got lots more concrete. it works for me since all that concrete acts like a big heat sink and keeps the garage cool in the summer and warm in the winter.