I've wrestled with this in the past. As a CS PhD student, I will be working full time as a web developer when I graduate.

For me it came down to either (sweeping generalisations):

1) Continuing research on interesting problems, or perhaps working for interesting companies like the Bearau of Meteorology or the CSIRO (the Australian governments industry research organisation). The problems would be intriguing, and you would feel very satisfied with what you have done most days at work. However when you get home, I imagine you would be pretty mentally exhausted, and may not find much time or energy to work on your own projects.

or

2) Working for a web dev company, where the problems are (not always, but often) relatively straight forward, and don't take too much mental energy to solve. Sure, building business apps is not the most satisfying job for everybody, but the people are great, the company is great, you get looked after well, etc. The best bit is that when you get home, there is probably more mental energy to work on your own side projects that interest you.

I like contributing to Open Source projects, and I also find that after a difficult day at work or uni, I don't have the energy to punch out an hour of coding when I get home. So for me, I'm currently leaning towards option 2.