have the option to head to Utah around Christmas, but I'm unfamiliar with the different climbing areas and camping options.
what is camping like in the NP's? any available in winter?
not sure where to start, other than picking up a couple guidebooks tonight.

what is camping like in the NP's? any available in winter?

The campground in Zion Canyon is open year round. It's much better in winter than it is in summer and winter weather in the canyon bottom is usually pretty mild.

The area around Zion is one of the few places in Utah outside the national parks that you can't just camp anywhere you want. There is a lot of private land around.

There are still plenty of places to camp and winter is usually uncrowded. Quail Creek and Snow Canyon (named for a person not the white stuff) are good places to camp in winter.

There are plenty of places to camp around Moab, most of them designated. Finding a campsite shouldn't be a problem inside and outside the parks.

thanks, Scott.
any must-see spots?

any must-see spots?

Basically the whole area and it depends on the activities you want to do.

In winter, Angels Landing is usually reasonable, sometimes not. For anything technical, you'd be better of with south facing. Plenty of rock climbs are in nearby Snow Canyon that are reasonable in winter. If you don't mind renting a drysuit (available for rental near the park entrance), rent one and see the Zion Narrows in winter. Very spectacular.

Most things around Moab are doable in winter. Even the skiing is good in the La Sals.

If going to Moab and Zion, take the scenic route via Highway 12 through Escalante and Boulder. Make sure to see Calf Creek Falls.

For technical climbing, Moab and Zion have plenty; too much to list. At a minimum make sure to see the Fisher Towers and climb something there. Nearby, Castleton is known as the quintessential desert tower and shouldn't be crowded then.

If I was going from Moab to Zion, I'd stop a night in Escalante. Better to see the slot canyons down the Hole-In-The-Rock Road than Calf Creek Falls. Lots of other things to see around Escalante, but bear in mind that I don't do technical climbing, so what I would do might be different than what you might want to do. Problem with Escalante is you need to have good info to see the best places and good info isn't always easy to get. I'll second Scott on renting a dry suit and hiking up to the Zion Narrows - one of my favorites. Problem is I've got way too many favorites in that part of the country, altogether they'd make maybe half a dozen one-week trips.