Cyclocross - Redline Pro or disk?

I am about to buy my first cyclocross bike. There is not much of a selection in Las Vegas - not much mud either. There are two 2005 Redline Conquests on sale a Pro for 900 or a Disk R for 1000. Both seem to retail for 1500. The parts are very simular, the shifters are different and the stem on the Disk is longer. The Disk has skinny tires and it says on the tag it is a 55. Redline doesn't make a 55cm bike, so I am confused.
Not the best service in this store - I don't really want to buy from them, but they have the bike and a great price. They don't however have any 29 inch tires I could use to replace the tires on the Disk.
I am leaning towards the Pro, is there any reason I should consider the Disk? Or should I order a different bike and pay more. There is a Felt dealer, but that is going to be 700 more dollars and all the shops have offered to get in whatever I want.
Other than that I am planning on picking up some Candy SLs and Cannondale Roam shoes off the internet, oh and a new helmet.

I simply don't understand why anyone would put a disk brake on a bicycle. Isn't the RIM a disk brake already? So you want to add the extra weight of the disk, the caliper mount etc. and then have the added drag of the pads all the time?

Get the Pro. It has better geometry and disk tabs if you find you need them later.

If you ride in an area that is dry, or at least mud free:forget the disc brakes. They are great for wet weather, but not great for wet muddy courses. Standard catileavers work great and are less likely to haunt you with mechanical problems.

That being said, I have disc brakes on my mountain bike and I love 'em.

You might also want to consider the Surly Crosscheck. You can find several bike shops online that sell the complet bike for around $900.

Phil T, I was in the same boat a few months ago when I was looking at buying my first cyclocross bike. I had never raced cx before and didn't really know much about it. I ended up buying the Disk-R because I wanted disk brakes. I know that's not the most popular thing to do in the cx world but rim brakes seem like a step backwards to me. Since buying the bike I've done two races. One was very wet and muddy the other was dry. I've noticed the disks work better in the wet/mud, but they have so much power and the tires are so skinny that it's really easy to skid. If I had to do it over again I would probably get the Pro and add disks later if I wanted. The things I noticed on the Disk-R are, lower bottom bracket, no top lever brakes, 50 tooth big ring, sloping top tube, road tires. You do get a carbon fork on the disk-r though. Honestly though I would ride both and get the one that felt better.
http://www.esaleomaha.com/BikePictures/Redline1.jpg

Thanks for the words, I went with the Conquest Pro. The store didn't have any candy pedals, so I have toeclips right now (boo) but should be riding in style in a few days.
I am excited.

The bikes have different geometeries as well. The Pro has more traditional 'cross geometry with a higher bb (and higher standover) and longer wheelbase.