For me, the choice would be the public school. First, I'd worry about her being the youngest in K. This is tough for most children and especially so for one wiht SEN.
Group speech therapy can work really well at this age. I've been involved with a group programme which didnt look impressive at first, but after a year, the change in the group was dramatic, and test scores (which I am not a fan of, but they are an indicator) across the board, improved significantly for all children. If she's still having individual speech therapy, I"d try out the group and see if it works for her now she's older.
LInks with SEN services earlier rather than later, The wheels turn slowly, and the sooner you are hooked up, the better for your dd.
The journey. That's a lot of time out of her young life that could be spent on better things! I decided against a preschool because of this very reason recently - I didnt want dd or her sister, or the new baby, to sit in traffic for over an hour each way.
I see it that a lot of the things you are losing, like, crunchy families, are supports for you rather than for her, that you can seek out elswhere - or maintain even if you are not at that school. As you are not burning bridges and can go back, I'd save the time in the car, the $$s, and see how it works out. This is a big year for your dd, and I believe that starting K too early for SEN children can have long term effects that are difficult to undo.
Interestingly, I just spoke to a friend about my own preschool dilemma. She has a son who is now 9 and sounds very similar to your dd. Her one big regret was the choice of preschool for him. He did much better in the P/S than the private nursery she paid such a lot for the first couple of years. He had gruop speech therapy plus individual SEN support, plus she got support from local services once he was in the P/S. That was not available to her - or not readily available - until he was in the PS.
Good luck with your choice!!