What are you planning on doing? Those are 2 complete different machines.
I'm currently using a RSC and it's as basic as you can get, it gets the job done. The take spool on this i'm using RSC actually turns the wrong direction for reverse wound lams which is a PITA.
I've used a Spire III when they 1st came out and maybe we got a lemon but we had alot of issues with it. It uses a digital display to let you know how much pressure your applying and if it's not calibrated correctly it can cause alot of issues with the lamination. with the RSC when you go full pressure it's locked in but with the GBC it's completely variable so it's hard to be consistent. Ours had 2 take up spools 1 top 1 bottom and was sold to us with the impression that you could set it up and laminate full rolls at a time and walk away.. Bahaha not in my lifetime.
I have a GBC Titan on a pallet under cover that I'm keeping for myself, I love that machine it's not fancy but it does the job consistently and I can depend on it and it's 15 years old!
Hope that helps if you have more question fire away I've used both machines.