I just received my openbuilds modular 1500x1500 table. I have it assembled, but I have not put a top on it yet. I was thinking I was going to do 1/2 mdf on top, but before I went to the store to get it, I wanted to get opinions on whether or not I should go with 3/4. I would like to keep the weight down, but if people have seen 1/2 being a detriment to working, then I will go with 3/4. Thanks!
Thicker is always going to be stronger. Its up to you what compromises you are still going to be happy with.
If you plan to do trichoidal milling or pocketing with a lot of fast short moves, heavier is way better. My torsion box table top is two layers of 3/4 inch plus all the upright pieces inside are 3/4" and when I cut small pockets that heavy table top is what keeps the machine from jumping right out of my garage.