Boy, I'm a little late to the party here! Hope I'm not too late to throw in my 2 cents.
I've sold property in both Blaine and Champlin. They both have their strengths and weaknesses.
So, much in the same way we don't share crime statistics and demographics with buyers because of the undue influence it might have over their decisions, I'm going to take the same stand here.
In order to answer YOUR question, I need to ASK a question. What's important to YOU??? Nothing I care about matters in the least. It's what's important to you that matters. I will give you my impressions based on what you think is important.
Much of it has to deal with where I grew up and now live. Roseville for most of my life and now residing in Vadnais Heights. I will always be a north metro guy because of this and somewhat biased to my side of town, and to me I just like the Blaine scene. As some have pointed out there is more to do in Blaine amenity wise. The growth potential is still there, and I don't really think it is that bad of a commute to either MPLS or STP.
I never go to Champlin for anything, but then again I don't go to Coon Rapids either. I think for most people who live in the suburbs we tend to stay in our own area. Most of the time for nightlife we go to MPLS or STP. Although I will say Roseville I still go to quite a bit. Como zoo with the nephews, state fair heck yea! and the Rosedale Mall still has a lot of what I do for more relaxing weekends like movies.
So, I will say neither Blaine or Champlin would be considered "hot spots" for nightlife and entertainment. It may just come down to housing and what you are looking for. The areas are similar priced, but obviously Blaine is a lot bigger.
Realtor North/NE suburbs
Drive around both cities for a while and see what you like.
Blaine has lot more housing Options. Housing stock is comparatively newer than Champlin. Blaine has lot bigger commercial,Retail, employment base than Champlin. Champlin is generally called a sleepers community. If you visit our site at http://www.HomesinMinn.com and go to communities. You will find all the information to compare the cities.