How to pick the perfect Nursery?

I'm in the midst of my biggest parenting decision to date.
We (The Tall one & I) have decided that it's time for the short one to go to nursery.  It'll only be two sessions a week until September next year, but we agree that it'll do him the world of good.
He needs the time with other small people, and much as I hate to admit it, he needs to learn that he can get along without mummy always being around.

So after much deliberation, we picked our top three choices, and today, we went to check them out.
I was assured by my sage, more experienced mummy friends that we'd 'just know' when we found the right one.  It'd feel 'right' and it'd be great.

Well, they were right, except that I got that 'this is the one' feeling, for two of our choices.  (Technically, I loved all three, but one has been eliminated purely because it's out of our budget.)
Dylan was absolutely no help, as he happily went off playing & exploring at both - basically so long as there are toys and snacks, I think he's happy.  He's quite easily pleased really.  Much like his mummy.

Both have slight downsides I can deal with, both have a whole load of positives that I love.
So how on earth do I choose?!

I shall do what I do best - mull it some more.  And hopefully make a decision before my head goes pop.