In my personal opinion, (and experience), whichever you chose it will give you at least a year of experience on the division. There are both positives and negatives to each choice: 1 year of ICU experience is a major plus that not many new grads have the opportunity for, but on the other hand, transferring internally may be easier, since the nursing managers already have an established relationship, as well as you already have an established relationship with the company. It just so happened that I settled on the latter, because of my relationship. And just for reference, I had applied to several hospitals outside of my institution and the hiring process was exceedingly more difficulty than an internal transfer.
It just depends on the type of experience you want during your first year. Transitioning from nursing assistant to RN has a major learning curve no matter which unit you're working for.