Both great games, but my pick is Deadpool. Metallica has a good layout, but it's also very vanilla...nearly identical to many other games. The rules are awesome up to Crank It Up. Then you realize that to get to EOTL you need to do it again, and again, and again, and again with literally no change to what you are doing to get to each. Don't dare start one of the coolest modes in the game, Seek & Destroy, or you will REALLY be back at square one. Chop chop chop that wood. But...the stuff you are doing is cool...and the CIU modes are very cool. So it's a tough call. The game has tons of personality, great art, and if you like the band, the music can't be beat.
Deadpool on the other hand has a very unique layout. Not quite as smooth of a shooter, but very satisfying with some unique shots. There is nothing else quite like it. Same with the rules...very unique. Yes, you do "repeat" the battles after Sauron, but with added shots to mix it up as you are battling each villain with Sauron. It feels like you are constantly making progress and building to the end, rather than running around the same track over and over like Metallica. This one also has great personality and artwork, and the A/V assets are awesome, especially if you like old school fighting games. Awesome game all around.
Can't really go wrong with either, but Deadpool gets the nod for the more unique layout and lack of wood chopping rules.