Agree with importance of going to visit some. There are excellent nurseries, excellent CMs, crap nurseries, crap CMs.
I've used one nursery and 2 CMs in total so far and my feeling is:
DSs CM at the moment is very educational with DS2, who is 2 years old. She is quite aware of his language delay, works at things to give him opportunities to develop it, keeps me informed with everything. She is also very loving and practical - I love the fact he goes to kiss her when we get there on a morning / leave at the end of the day. He has also formed very close bonds with the CMs children, they are almost like a second family to him.
DS2 at 4 goes to a nursery, which is also brilliant. He mixes with a lot of different children, does some structured group activities, lots of messy play, loads of outside space and likewise has formed some close relationships with the ladies who work there.
I am sending DS2 to the same nursery when he gets to 3. He could go now (and it would save me £9 a day!), but I feel like he is developing more at his CMs. The nursery DS1 goes to is great, but I feel they get more benefits there from following instructions, how to socialise and get on with other kids, learning things like putting away after themselves. Basically, getting them ready for school.
Both CMs and nurseries do similar activities - singing, messy play, going out and about, role play, free play with toys etc. I just feel that the one-on-one relationship DS2 has developed is right for his age right now. But I can see a time when he will benefit more from the structure / more kids environment of nursery.
Incidently, DS1 went to a CM years ago, but I wasn't too happy with her!!
Sorry for waffle - you'll know it's right when you find it, whether it's a CM or nursery.