We're planning a trip to visit friends in Sundance WY and spend time in some great parks. We've got 5 days allocated for visiting parks. While researching possibilities, I found this article which advises that Shoshone National Forest is better to visit than Yellowstone: https://www.islands.com/1817493/shadow-yellowstone-crowds-shoshone-national-forest-trails-mountains-hidden-shadow-america-alpine-lakes/
If you've visited both, I'd love to hear your opinion. For us, one advantage of Shoshone is that we'll be approaching from the east and Shoshone is closer than Yellowstone. The one difference I see is that Yellowstone has the geysers and Shoshone doesn't.
Also thinking about visiting Grand Teton and Mt Rushmore.