I have had both. IMO Grand Slam- I did not like the frame...too much weight and it kept sliding up my back when trying to sit down. Pocket layout was good. Not a big fan of large horizontal pocket on the right side. Cushion was comfortable. I gave it to my brother who eventually just took the frame out. He was actually trying to deploy the legs when a turkey he was working slipped up on him. He came to my house not too happy....
Time and Motion- I have had 3 Ol' Tom vests- 2 Essentials and 1 Time and Motion. Very light weight, however did not like the way that they felt when loaded. It seemed to me that it was just not sturdy enough to keep comfort with a bunch of stuff in them. The seat was comfortable, but tended to slide on me when sitting down. Also, the magnets holding the seat up were inadequate and anytime brush came in contact it would flop the seat down....I did have some issues with the stitching on the first Essentials I had, but all in all it held up well.
I have a Tac Tater 2 and I have no problem putting pot calls in the pockets (then again I only carry one with me to the woods). In fact, IMO it is the most well thought out vest I have ever had. The one complaint that I do have, that can probably be fixed with adjustment is that the bottom part of the cushion is hitting me in the rear as I walk. Probably just need to tighten a strap or two.