Agree with most - two days at one is better - we liked Zion - prettier, better facilities and better chance to see park. Bryce is nice, but because of the layout, bus after bus after bus of tourist come and are dumped out and make it difficult to see the park or even hike it. Do NOT miss the drive from t. Carmel Junction coming into Zion from the east on SH 9 - it's dramatic coming out of the tunnel - I think the requirements are
here for prohibited vehicles - usually you will just have to wait at entrance where rangers will radio ahead and create one-way traffic to allow for enough room for larger vehicles to pass through.