We have done it both ways.
The 1st year we ate at Chef Mickey's and then headed over to MVMCP around 6:30ish. The wait wasn't bad at all and nowhere close to what lines are like at park opening even.
The 2nd year we at CRT and was able to finish dinner right about 7:00 and able to beat the crowds to Fantasyland since they block it off until 7:00 and try to keep people in Tommorowland. This was nice however we missed the entire experience to walking in and having snow on Main St.
To me, I would rather have a small line and have that magical experience. This year we are eating outside of MK.