I have used both types of childcare for my girls (and still do).
Both have pros and cons, and whether they are pros or cons for you depends on you, your job, your child, your back-up plans and your local provision.
A good nursery is better than a crap CM and a crap nursery will be worse than a good CM. The tricky bit is finding a childcare provider whether nursery or CM that ticks all your boxes!
My advice would be to visit lots of places, both nurseries and CMs. Get cracking as some will have waiting lists.
Many of my reasons for wanting to use a nursery were similar to Maisiethemorningsidecat's - I am not in the sort of job where I can arrive late, leave early, take time off at short notice, pick any annual leave periods I want, etc, so I needed the "reliability" of a nursery. I don't have the ability to find alternative childcare easily if a CM were to be on leave, ill, or unavailable.
My childcare needs have changed slightly as they have got older - DD2 now goes to a CM after school, whilst DD3 is at nursery/preschool. The nursery is brilliant, even in the baby room (ie under 2s) they have activities, themed in the same way that thebody does with her mindees, a huge outdoor space that they use all day every day whatever the weather, lots of different areas so that the children can move around between activities, a meal room, a sleep room, bathroom and shower facilities, and lovely caring staff that range in age from school leavers to retirement age. There is very little staff turnover and most have lots of qualifications or are working towards them.
My CM is also brilliant, she is flexible, kind and caring with DD2 who has SN and is disabled, and I couldn't go to work without her 