Addai has "looked" better to this point, but we need to keep a few things in perspective. That Indy offense has made a lot of RB's look great, and some of those RB's have moved on to other teams, where they haven't been half the RB. Really, they've developed somewhat of a Denver complex, as almost any RB looks at least somewhat decent in their system, and good RB's look great.
When it comes to NE's rating Maroney higher:
Well, it's well known the Colts also rated Maroney higher, but NE pulled the trigger before the Colts had a chance, and it's also known that Mike Shanahan loves Maroney.
If you watched Maroney run in college you would have seen quite a nice back, and if you've watched him the past few games you'll notice some pretty good runs. Watch his runs & receptions against the redskins, and his runs against the colts, he's showing signs of damn good ability. He's been running with power, speed, and balance.
NE needs to develope his receiving ability more to fully realize his potential, and frankly I'd like to see what he can do with more carries. Some people seem to forget a lot of yards RB's tend to rack up come toward the end of the game, when the defense is tired. I'd like to see what He can do in those situations, a little more.
Also, Addai had his injury bugs in college, hopefully Maroney's now put his injury bugs behind him, as well.