I am having the same dilemma. A private nursery where DS2 has been since he was 1.5yo (now 3.5yo) or a state pre-school with double pre-school hours (for full-time) and afterschool club in the same premises (DS1 goes there after school).
I was sure that I want pre-school when I applied, because my DS2 is one of the older children, so for him to mix with the same age group, more experience staff, more stimulation, an amazing garden and pick-up of my both DC from the same place. Downsides: I would have to provide packed lunch every day and holidays will have to be arrange separately.
Private nursery - children of all ages (they are in separate rooms but also mix together), young staff, miniscule garden, sometimes looks very chaotic and disorganized. There used to be high staff turnover, but not anymore. But... DS2 is happy here, it has a family atmosphere and it feels as the staff is making an effort. Plus it is open 8-6 51 week a year. Plus easy parking.
I don't know what I am going to do. I will probably still move him to the pre-school, though as the time passes, I am increasingly unsure. I know a child that has been moved to the same pre-school last year and he is thriving.
Any experiences welcome.