Grand Canyon or Yellowstone for 2015?

I thought that painted desert and petrified forest was sort of disappointing. grand canyon, a big hole, sort of a yawner after first glance. Had a friend who also went there after me and said yep, you walk up, say gee that's big, and leave. sort of want to see Palo Duro but way out of the way for my Houston trips. I certainly wouldn't waste time seeing it if you are going to the grand canyon. Sort of like when I visited the Wisconsin Dells after seeing the rocks in the South West. :)
I've been to both North and South Rims and I sure didn't see more to do on the North side, unless you want to get a second mortgage and see the glass floor overlook.
bumpy