I have done both-Part 121 for many years (left as a Boeing Captain) and Part 91 for the last 5. No comparison. 121 builds up your time, your confidence. Part 91 tests all the things you learned in the years of 121 every flight.
Pay in a good Part 91 flight department is much better than 121. Besides salaries that top the wide body 747 Captains, the benefits cannot be beat.
Warm destinations in the winter, Asia/Europe in the summer.
There are 3 types of corporate flying:
Part 135: enough said.
A bad part 91 job: good while you are looking for:
A good Part 91 job. Time off, mentally challenging and incredible job satisfaction.

If you just want to fly from A to B, corporate is not the way. If you want to challenge yourself both personally and professionally everyday, it does not get any better.