A:Answer Hi xmasgift,
The 1st thing you need to consider it is weather you need a companion for your phone or need watch which operates as a stand alone. If you carry your phone around on you, then there is very little need of cellular data. But if you want to leave your phone at home and need your watch to operate a a stand alone device, receive call and play music on it own then definitely go with the cellular version.
Moreover, I would like to point out the second thing is, you need to get a data from a carrier (with monthly cost from $10-$20) and the cellular apple watch is more expensive than the regular GPS version.
Make the decision based of your needs.