I put a folding table up on 12" risers for cutting. I move it to 4" risers for when I'm quilting to use as an extension of my desk.
As someone else pointed out, it really depends on your height. I'm 5'11" so a kitchen counter is uncomfortably low for me. If you are able to visit a furniture store in your area that sells the kind of bar or table that you are considering purchasing, I would recommend bringing your rotary cutter with you. Leave the blade retracted/covered, but try out the movement to see how comfortable it is for you to have your arm at that height.