I've been using G2BG spray for more than two years, and I've used the spiking gel for several months. Here is what I've found:

The spray works great for me with a skin system. It usually loosens up overnight when I sleep, but it's a 2 minute job to reattach. I always hated the long involved clean up of lace and glue residue.

The spray did not hold on lace for me.

The gel seemed to have a slightly longer/stronger hold and easier clean up, but I would warn you to test how it reacts to your body chemistry/perspiration. I'd used it for a good while, then one night after a fresh attachment I had to set up our band's gear in a hurry. The place was hot, and after an hour I was dripping wet. I thought something felt funny, when I checked I could slide the entire piece around on my head. I got through that night by putting on a ball cap, but it could have been disastrous. I never had this happen with the spray.