To quantify, as both military and 121:

Pros:
Mil guys will learn the aircraft very well and very quickly.
Mil guys can fly very well, have great SA, and can make great decisions (relative to their experience).
Mil guys are great at the flying aspect, but I would say that the actual flying part is about 40-60% of the job and management is the rest.
When I started at the regionals I had 750hrs (mil TT r-ATP). First day of OE was 5 legs ending in Mexico. I did fine, the check airman even said he thought we would have to canx a leg because I would be so far behind, but I wasn't. I also wasn't the captain I was an FO. That being said, 2 years later I still wonder if I am ready for the left seat.

Cons:
You typically have 30 mins once you get on board the aircraft to plan, set up and release the break. In the military times are important, but not always the driving factor.
You operate with the fuel dispatch gives you. You can't just throw on another few thousand pounds because the weather isn't great.
Winter time operations in the 121 world takes time to understand and get used to.
Mil guys are used to 1-2 flights a day, doing 4-5 does wear on you and attention to detail after 3 flights starts to degrade.
Taxiing at large airports, I've been a regional guy for 2 years and I still hate going into ORD.
Customer service is a whole different conversation.

I hope this helps to highlight some areas that are different from mil flying that needs time to learn. This is not all of the problem areas, just a small list.