Comcast

The cost varies depending on what services we use because it is all bundled with cable.

They could provide more consistent service and greater speeds.

It's okay. I would prefer not to use comcast, but they have the most reliable internet.

After contacting five other providers and having them come out to my home, review my needs and offer their recommendations for a good security system, we chose Xfinity Home Security.
They were thorough in their analysis and provided a true state of the art system that will run even if your power goes out or your cable is cut by an intruder (the system runs on battery back up for 24 hours and connects via cellular instead). Plus you get a total touch screen (like a small iPad) next to your bed, or were ever you want it, with 3 emergency buttons you could hit in the night (Police, Fire and Ambulance).
You can run your whole system with your mobile device or computer remotely from anywhere and can turn on or off any part of your system room by room if you want... many companies claimed this but upon closer examination they couldn't deliver including ADT. Also there is absolutely no lag time or delay between your device and the system, unlike many others (some people were complaining about having to wait 10 to 15 minuets to get into their house).
Everybody is going to charge you something for the use of their equipment, but Xfinitiy's was less, especially for what we got. No one else could provide security for our garage because of the cold in the winter, but Xfinity could. Plus they only charged $29.95 a month for the first 2 years $39.95 for the third year... half the price of most others. After which you own the system and can negotiate a low monthly rate.
Several companies knocked Xfinity's equipment though they didn't know what they used and said it was some foreign product (they use Honeywell by the way).
We have only had the system for a few weeks now... so far no glitches and we are feeling a lot safer.