I've used both Paperclip and Carrierwave, and if I were you, I'd go for Carrierwave. It's a lot more flexible. I also love the fact that it doesnt clutter your models with configuration. You can define uploader classes instead. It allows you to easily reuse, extend etc your upload configuration.
Did you watch the Carrierwave railscast? http://railscasts.com/episodes/253-carrierwave-file-uploads
Paperclip is not a bad choice though, it's been the "best" choice for a long time. But Carrierwave definitely seems like the new generation ;)