Our daughter, who is introverted, much prefers older kids. Looking through the posts on this thread most of those kids who'd prefer younger/same age kids seem to be extroverts. I wonder if for an extroverted kid, who likes to lead play and be in the thick of things, older kids just aren't as satisfying? They're possibly already getting to play their own choice of games, they're able to be take control of the kinds of interactions they are having etc. Where as for introverted kids, older kids offer a chance to play the kinds of things they want to play (simply be being more aware of the same themes and ideas) but can't necessarily negotiate with same age kids to play. I have no idea if this is actually the case, just my thoughts!
Having said that, we have had the same experience as you too, Wren. Our dd plays beautifully with a couple of friends' daughters who are a two or three years older - when she and one of them are together one on one. But as soon as there is more than one, naturally the dynamic changes and dd is left struggling to participate equally.
