Hi Lucynewt
Can't give you advise on what you should do but can tell you what I did/felt when I went back to work.
I went back to work when my daughter was 13 months. I seriously considered returning part time and dreaded going back. I felt really immersed in the 'baby world', connected to my local community and felt I'd miss all the nice things my daughter and I did together.
However, I ended up going back full time for the following reasons:
My chances of promotion / a proper managerial job would be = 0 if I went back to work, even four days a week (so I decided to give it a year to see if my career prospects were as good as they were before I went on maternity leave, they were, and I've stayed full time. If that changes I will definitely consider going part time)
My daughter was, at 13 months, ready to start developing away from me and I found a really good nursery I was very happy to leave her in. There is a BIG difference between a 9 month old and a 13 month old. At 13 months she could eat on her own (messy, but even so) and walk. She thrived at nursery.
We started having very active weekends. When I stayed at home with my daughter, the weekends were mostly for relaxing, now we do lots of stuff, including swimming, gymnastics, trips etc; things we may have spread over the week before.
A final piece of advice - get lots of help e.g. cleaner / au pair etc if you can at all afford it, it ensures that you get to spend time with your daughter when you are off work, rather than doing all the chores (and see also the excellent thread on organising yourself if you are working (full time))
Good luck with your decision!