Boulder has some great places to eat, drink, and be merry. Some great music venues and the Pearl Street Mall is a great place to hang out on a Sunday afternoon. If you live in Louisville all that great stuff is just a few minutes away. The house prices are more reasonable, as well as the local taxes and regulations.
I moved there in the early 90's as house prices were starting to skyrocket. Imagine my surprise when the tax assessor lowered the mill levy so that even though my home appraisal went up, my property tax stayed pretty much the same!
Also, at the time it was the only city in the area that didn't require guns to be locked in a safe when not in use, etc. Boulder and Lafayette (on the other side of Louisville) seemed to be trying to outdo themselves in nibbling at the 2nd Amendment, but Louisville wasn't having any of it. Louisville has its own quaint downtown with a classic bar and good restaurants and it seems to be a more family friendly place than Boulder ... unless you're talking about the Rainbow Family which is one family no city should want to be friendly with.
Thanks - Louisville sounds pretty good!