[atheistwithfaith]

If you were entering a field in Japan related to your work then I'm sure the portfolio would be of benefit but for any other employer they wouldn't know how to interperet it (if that's not their usual way of assesing candidates).

There are many mature JETs so I find it doubtful your age would be a large hindrance - they would be more concerned that you were able to leave behind your life at such an established stage in your career. From the perspective of the actual job you would likely have a lot more life experience to bring to it and to share with your students than someone straight out of college (21-22 years old).

As for what degree to do, I think it would be more important to do a degree which you can use - what happens if you have invested all that time and money and don't get into JET?

I know your feeling about thinking you would regret not having gone for it, I was undecisive for a long time about whether I should go on and do a PhD in my current subject after I finish my degree or whether to just go for what I really want to do (JET) even though it may effect my chances of getting into a PhD. I decided its such a unique opportunity I can't turn it down, so I am going to apply for 2011 entry (fingers crossed!).