Definitely play both, a lot, and then go with what you like best.
For me I would pick the Hobbit due to its build quality, value offered in its features and the incredible ruleset developed by Keith Johnson. The Hobbit offers over 30 modes, several multiball modes, 3 multistage wizard modes and a super wizard mode for completing everything is supposed to still be coming. A lot of things sold me on the The Hobbit but its ruleset and code support is one of the biggest reasons I bought the game.
I may still by a Ghostbusters premium one day but it will depend on if the games rules are expanded anymore. Right now many of the games cool features such as the Ecto Goggles and Slimer mech are under utilized in my opinion, especially the extra movement of the premium slimer mech. Also, having to play modes always in the same order can get old after a while.
I hope that Ghostbusters gets a few more big code updates that expand on existing game rules as I think it's one of Stern's coolest looking and most feature packed games yet.