My 2 have been to nursery. I have to say that a huge amount of my parenting stress comes from whether I'll be able to leave work in enough time to pick them up. Our nursery runs 730-1800 and it still gets a bit hairy at times.
Dd is 10m and been at nursery for 2.5m. She has been ill since she started - colds, ear infections, hand foot mouth, the usual. I've had to take a day off for her already. But, nursery are great, she's happy and my son learnt brilliant social skills from going.
You'll almost certainly end up with more time off with a child sick off nursery than an ill nanny but you never know.
Friends with nannies have either had a recommendation (ask about, nannies all seem to know each other, so if you have friends with a good one, ask her) or used an agency.
I really don't think there's one right answer. But with those working hours (presumably leaving half an hour before and getting back later) I'd go with a nanny.
Useful things to consider are nanny share and nanny tax and finances. On average, here, having a nanny costs a little over twice what a nursery costs.
Maybe go and see a few nurseries and see what you think. Be warned though, I booked for mine at 12 weeks pg, the good ones book up early. If you're unsure, put a deposit down and hold that place! If you don't like the environment, you'll have your answer.