I considered the options very carefully when I returned to work 3 days a week when my son was 12 months. I had always thought I would prefer a childminder for him, as it would provide a more home from home environment.
However, when I gave it more thought, I did not like the fact that you do not have any control over who else may come into contact with your child when they are with a childminder, and also did not like the fact that they could be in the car with the childminder 2 or 3 time each day on school runs, supermarket shops etc - both due to safety and general stimulation.
I chose a nursery which I am very happy with - my son has never cried when I've left him there, and genuinely seems to love being there, gets loads of stimulation from lovely staff, and has mastered things I thought were beyond his age. I also think it is a very safe environment compared to other forms of care.
Even if I didn't work, I would put him in for a couple of sessions a week as I feel he gains so much more from his experience there than I can offer at home. I am amazed by the amount of work that goes into caring for and developing my son - I am happier with my choice than I ever thought I would be before sending him there.
I visited about 8 different nurseries however and the standard of care varied massively - 4 out of those nurseries I would never used in a million years.