I would take Kiss all day. Others opinions will vary, this is pinside right? But I'll start the discussion my my personal pros/cons, knowing that someone will get very upset about it either way. Caveat: I haven't owned either game but have played them both quite a bit on location.

Kiss
Pros:
Code has had a major update making for more balanced scoring and progression. Combo shot multipliers are fun!
Sweet sweet center ramp shot that feeds your left flipper for some aforementioned combo action.
Unintentionally hilarious Paul Stanley callouts. "I'M GONNA DOA LITTTLE NUMBAH FOR YA NOWWWW"
Kevin O'Connor art package
It's a John Borg game... nuff said.

Kiss
Cons:
Gene head shoots balls down right between the flippers, more of a problem on the Prem/LE. I think this can be adjusted/tweaked to occur less frequently, and code addresses this by making a short ball save *usually* active when this is happening to reduce cheap drains.
I'm trying to think of a polite way to describe the DMD animations other than saying they're maybe the worst since Transformers. They just look bad.
You have to be ok with listening to Kiss songs... all night, and ev-er-y day.

Ghostbusters:
Pros:
The obvious: this is a pinball machine based off the movie Ghostbusters.
ZombieYeti art package! Home run! Game looks great.
A lot of design elements here: Cool Slimer mech/toy. Ramp that goes under the playfield, captive balls, cool toys and models.
Callouts and sounds are great and really tie in to the theme ...but maybe lacking in variety.
Magna-slings!

Ghostbusters
Cons:
Ladder mode progression. To me, not fun. Hearing "who brought the dog?" at the start of every game gets real tiresome.
Code: Stern says another update is coming. Wizard modes are ...eh. Starting modes is a chore if you miss your skill shot. Skill shot awards and bonuses can get way out there in terms of scoring balance.
Cheap drains... hopping over inlane rails, airballs off everything, scoleri target bricks, slingshots close together tends to send a lot of balls to the outlanes, oh and I should mention the flipper gap: personally I'm ok with it but others not so much. Still, can be a really frustrating game to play and doesn't feel as good to shoot as Kiss (or any Borg game really).
Magna-slings!

That's my personal take. Don't take my word for it, get out there and play some pinball! What I like and what you like might be totally different.