A good frame is much more important than the decking thickness. I personally recommend using 3/4" plywood and then glue on a cut sheet of 1/2" plywood so you can install T-tracks into the top. The T-tracks are 1/2" thick so they are flush with the top of the plywood. I use a 6" on center spacing for the tracks, which works well for me. I have most of my tools set on 1" oak bases that will slide into a T-track.
So If I want a press, a vice, a lube sizer, a case trimmer, etc. etc. I can simply and quickly slide it in and lock it down. When I am through I unlock and slide it off and my bench top is free for the next project. I have done this for friends so now if someone needs to borrow a tool any of us can simply slide the tool into our tracks as they are all on the same spacing. I glue and screw down my tracks and have never had one loosen.