Most junior ERJ DEN is an August hire. Most junior CRJ DEN is a September hire. Most junior CRJ COS is an October hire. It's February, so you're likely to get COS right as you finish up IOE. The others would be a month or two of commuting to reserve.
Generally, if you're on reserve on the CRJ, you'll probably fly quite a bit, especially if you put yourself on call first. On the ERJ, not so much.
Another consideration if you plan to live in Monument...the drive to COS is a whole lot easier than the drive to DEN. Plus, the DEN employee parking lot is a solid 30 minutes from the time you park to the time you are through KCM. It's a LONG shuttle ride. Then another 15 minutes to take the train and walk all the way down the B concourse to get to the ghetto gates we use. When you pull in to COS, you're 5 minutes from the gate. I live 10 minutes south of Monument, and when I was on reserve in DEN, I had to be constantly ready to leave the house in 5 minutes and had to hope there were no accidents/unusual traffic.
With the CRJ you'd have to go to SLC for at least a month though. They do have CRJ sims in DEN, but most folks end up having to do sims in SLC. On the flip side of that, in SLC you wouldn't have the family responsibilities getting in the way of your training. I'm no dummy...I did very well in college and Navy flight training, but I'm really glad that I could just drive 10 minutes to a hotel to start my homework every night. I think if I'd had an hour+ commute each way, plus the distractions of the house, I'd have been in real trouble. The training wasn't hard, but it was VERY time consuming. They did restructure the training in the last few months though, so it may be quite different now.
Honestly, if your goals are truly to fly and limit commute, I think your best bet is CRJ COS by far. A month in SLC where SKW is paying for your hotel and you can devote 100% of your focus on training is MUCH better than a month commuting to reserve in ORD, when the lodging is on you, and they won't be flying you much.