Hospitals in my area offer the traditional 8's as well as 12's, in every unit. As for what nurses like to work, nurses prefer whatever shift they work...that's why they work them!
And as for medication errors, a study was done at my hospital, and there were no greater percentages of errors for the 12 hour shifts than the 8 hour ones. Actually, the very slight difference was in FAVOR of the 12 hour shifts: something about more actual days spent at work (less time off) contributing to a very slightly higher rate of errors. I'm quite sure that the people who work 8 hour shifts (and are used to that) are quite tired at the end of their shifts. And those who work 12's (and are used to that) are also tired, but not so much moreso than the others. At least, that's how it is for me: I've worked 8's and 12's, and when I did 8's I was tired at the end, and now on 12's, just the same tired. Only now, I have four days off to get UNtired
Don't know how accurate the error assessment is either way, frankly, but I wouldn't look to 12 hour shifts as Medication Error Central.