We were in Glacier last year. Follow the link in my sig for pictures.
We were in RMNP in 2014.
You can't make a wrong decision. Glacier is more "epic", but that comes at the price of MUCH more driving. We have lifetime memories from each park and would trade away neither.
I drove "GTTS Road" 3 times over and back. I never have issue with scary drives (no problem towing the Million Dollar Highway) but by the end, I would not drive GTTS again. I was frazzled. That said, I thought the pricing for the red bus tours was crazy when adding up a family of 4.