It's not even close for me. Mapes inlays are the clear winner. The inlay on Mapes is near perfect IMO. Vintage, simple, clean. Classic. The Caesar's inlays are absolutely hideous to me. Giant inlays with pictures of statues? No thanks. Those are almost as bad as the PNY inlays. They look like those limited edition chips that I can't wait to get rid of if they're in my stacks at card rooms. The first chips into the pot for me.
Also, for those of you who think the Mapes are only popular because of their TRK colors and edge spots, I'd like to point out that the Money Tree TRKs don't have near the demand as the Mapes do, despite being in better condition. The reason for this is the inlay, obviously. There are also several tribute sets out there with tweaks to the Mapes inlay.
Of course, everyone has their own tastes, but for me, it's Mapes all the way.