Everyone's experience is different, but I am a big fan of the mirena IUD. I had lots of problems with the pill - killer migraines and unbearably tender breasts most of the time. I used a diaphragm for a long time too, but got an UTI about every 2 months, which you can imagine is a bummer. I had the mirena before deciding to have a baby, and was able to get pregnant within 6 months after removal (btw, I was 38 when we conceived). Now, 3 years or so later, I just got another mirena. After 1-2 weeks of spotting with no cramps, I feel totally normal.
On the one hand, it seems only fair to let your husband bear some of the burden of family planning, but on the other hand, as simple a procedure as a Vas. is, it is still an invasive surgical procedure that is not easily reversed.
There are risks with both procedures, so you just have to decide which will meet your needs the best without unacceptable risks.
Good luck with your decision!