I'm currently 29 weeks with number one and mine was a bit of both. We've been together 12 years and married for 3 and I'd originally promised H we would start TTC after a year of marriage. As it was I'd only just started a new job and head ruled because I didn't want to get pregnant straight away, I left that job after 6 months so we were back in the same position again and I told H that I really needed to build up a career for myself first. So again my head was ruling.
Then last Nov, my H was going off to Dubai for 2 months for work and we were <ahem> fooling around and had a bit of an accident. I said I would get the MAP and H asked me not to. We ended up having a big chat and H said he didn't want to wait anymore. That 2WW seemed to take an age, because I kept swinging back and forward between it being a good and a bad idea. When AF arrived I was gutted and that gave me my answer. It took us another 5 months after that to get our BFP and I couldn't be happier, I'm very glad my heart eventually took over!
I do think there is room for a bit of both in the TTC decision, there will very rarely be a 'perfect' time to try, but there will be times when a baby might be a really bad idea. Then again everyone always says you just learn to cope, don't they?