Should I change jobs?

I'm took a job a few months ago that pays low for my field. I know I could go out and get a 10% bump.

But it comes with a pension after 10 years, which is about when I hope to retire. I pay 6% of my pay in to the pension. Also, there's a hard to explain surcharge of another 6% on my salary due to some tax regs (can't explain without revealing where I work).

I really like the job, the management, the co-workers. But I'm very, very marketable in my field, so I can easily get other offers. Should I leave and put that 12%+ difference in a 401K or stay because I like the job, I'm immune to being laid off(this place is unaffected by recession), and the pension is guaranteed (the union says its fully funded).