I own both.

While HS is a fun, relatively fast playing game. It is limited in its ability to entertain. Get big points off the loops and run the light for multiball. Escape and score the jackpot to win the progressive. That said, it is a BLAST to play with others. Infact, I will rarely turn it on, unless someone wants to play with me. The lack of a ball save makes ball times short and the games can get real competitive! "504 to dispatch, he got away"

Freddy, on the flip side is far more of a one player game. Long ball times, and if you can get through all the nightmares, the Final Nightmare is a lot of fun! The Boiler room is a fun way to start modes and the game is packed with cool features. Talking, taunting fred head - claw flipper (even without all the fingers, which they never have) is a cool skill shot to try and master - up kicker - etc. No ramps is a down side, however if you are willing to play a game that is less based on flow and more on getting through modes, nightmare is very cool. With Battle based multi-balls (work down his health to defeat) and a ton of them, the game is real fun and exciting to play solo. "1...2...Freddys coming for you"

All of this said, they are a great combo to have next to each other and I recommend picking up both if you can. Generally, both are about the same price 1000-1500, so you can get both in the price range of 2-3k. They both have fun game play, and you won't be let down by either. Provided you understand that they both play drastically different.