When is best to start daycare? 10 months, 12 months or 18 months? (Ontario)

We have a potential daycare spot which would be available when my daughter is 10 months old. She does not nap well and feeds to sleep still at 9 months. I am taking 12 months leave with option to extend if needed. I thought if we start at 10 months, I would be able to slowly transition her but I’ve heard a slow transition may be harder. I worry about illness and not having all her vaccines yet. Would 12 months be better? We are in Toronto where spots are hard to come by but I want to ensure she develops a secure attachment and healthy development. Any experience or advice is appreciated!