I have both - and.. yeah, they are very different games. If you like Pat Lawlor's games where they are fun to shoot, have lots of combos, and are mode-based, but not terribly deep - then that's DI. Awesome, very fun, amazing game. DI is PACKED with mechs and the type of mechanical, physical stuff that sets pinball apart from video games.
Hobbit is a journey - I don't mean a slog, where you're chopping wood - but it is *very* immersive. Dialed In is similar to playing a really fun video game (lots of video game influence with the bosses, health meters, etc) - while the Hobbit feels like you are IN the game.
It has 30-something modes, which is at least double the next game (Houdini), AFAIK. THey are all fun, and they are all really clever. The modes which come available a bit later on in the game use the monster mechs extra effectively: when you are in a battle, you are bashing into them to fight off the attack, whilst still trying to make regular shots. Other times the monsters are used as barriers to change the playfield and force you to re-think your available shots. AND THEN there is this diverter which comes out of nowhere on the ramps, and makes the ball come flying back at you in a very tight turn (similar to the Star Wars Tie Fighter shot [i think]). That is awesome when that happens.
Add to that actual callouts from the game, a Gandalf sound-alike, tons of actual music from the films... and a bunch of very fun wizard modes. Oh, and killing Smaug. Not even the Master Magician mode, nor is it the "end" of the game, but it is amazing when you do it.
Previous criticisms of the game included that it would get super long (this was true), the multiballs were coming up too often (also true), the playfield is "wide open" (I disagree on this because of the phenomenal use of the monster mechs, and the fact that a lot of the game mechs are placed at the far outer edges of the PF but still do their jobs just as well as if they were in the middle)... and it generally just wasn't as fun as it probably could be. I agreed with that after a while. UNTIL 3.0 came out. Holy crap.
I sold my Hobbit last year - just bought it back. And I am now getting ready to sell DI (which I really enjoy, just not *quite* as much). Hope that helps.