Hi, as a cacher who has used a phone, a cheap GPS and now two paperless GPS machines i certainly know what we would use.
We often use our phones if we are not actually out anticiating on doing lots of caching. The difficulty can be though that the phones battery often runs out really quickly and normally do not have the facilities to charge it.
The advantage of a GPS is they run on AA batteries and it is easy to change them and contine
We currently have two GPS with Paperless caching facilities, this is so much easier as it means you have access to all the information on the cache page including the hints and the logs from previous finders.
We have an Garmin Etrex 30 and a Magellan GC Explorist. we love both of them in their own special ways.
Hope this helps