Utpoian we have an ofsted outstanding nursery near us which you have to put your child down for pretty much at conception if you want a place age 1. Lots of people use our nursery as a stop gap, until their place comes up. I'd say about 50% decide to stay rather than move.
By September next year you'd pretty much be looking at preschool point anyway, and the 3yr funding. People will move then anyway (probably why the place will become free) as they decide to use school based preschools etc, or like us moving A in December to be nearer DD's school.
I would go with 2nd choice, see how it is in reality. When a place comes up at 1st choice you can see how you feel- move or stay depending on how you've got on, whether DC2 will get space when you need it etc.