Beaver Creek: Main park (the Rodeo)- Seldom rail features, 5-6 (maybe even 7) jump line. Each jump getting bigger pretty quickly, I think the last one is about 65 ft. Opens Mid-December, I'm not really sure when it closes. Relatively slow laps.
Vail: Golden Peak- 5x or more rail features than Beaver Creek. Small & Medium jump lines. Usually everything is set up by February. I think it usually doesn't open until early January. Big jump (sometimes 2) and large rail features at bottom of park. Typically well maintained up to closing day. Quick laps.
Vail: Bwana Park- 20ish rail features and 2 small jumps. Open Mid-December. Pretty quick laps.
As a guy who doesn't ski either park a lot, I personally prefer the set-up of the Rodeo (I don't really hit rails). Golden Peak is probably "better" though to most skiers. And to state the obvious-Keystone and Breck's parks are significantly better.