I think it depends most on what type of unit you will be on, and the acuity level of the patients. On high-acuity units, the "busyness" and learning opportunities might not differ much, if at all, between days, evenings, or nights. When I was in nursing school
, I did all clinicals on days, except for my capstone, which was primarily on nights with an occasional day shift - the acuity of the unit was such that I was equally busy and challenged in both settings.
Here is another huge thing: Your experiences in clinical are 100% what you make them. It's all about jumping in with both feet (safely, of course), and getting experience communicating, organizing your time, and performing nursing skills. I'd be willing to wager that you could have GREAT experiences on days, or evenings.
Best of luck!