First, let me say I'm not the smartest football mind at all, I've never played organized ball, and just been a fan of the game for about 10 years now. With that said, here's my take on our two RBs.
I've been a fan of Donald Brown since he got to Indy. While he didn't have the greatest of results, I always thought that was more due to the way he was being used and not because he just wasn't that great. I believe we are seeing that now. (He still sucks at pass blocking though, that'll never change, IMO.) He's a fast, shifty, change-of-pace back, and now we are allowing him to do just that; take quick cuts and get up the field, it's just a thing of beauty to watch him run now.
Now as for Trent, I'm from Tennessee, big SEC football fan, and I was a big fan of the trade for him. I thought he was going to be a great back in the NFL, and his rookie year I kept up with him pretty good. When I was on the way home from work one day and heard about the trade on the radio I was ecstatic. I felt that this could make a huge difference in our season.
Last night was the first time this season I've second-guessed the trade. I have many friends who are Tennessee Vol fans, who hate Alabama and therefore love to criticize the trade (they are also Titans fans so they get to ridicule me as a Colts fan with an Alabama RB). I've tried to defend it time and time again, but last night it seemed it was for naught; Trent just couldn't get it done when Brown could. I was finally convinced it was a bad trade.
Then I really starting watching the game, and I think I might have an idea why they were having varying success. It's no secret that Brown is the quicker of the two backs, as well as the smaller of the two. It's also no secret our line (interior especially) is absolutely awful. In my ignorant football opinion, I think the reason Brown is doing better than Richardson is because of our abysmal line. Our line can't seal blocks, and can't make big holes. Brown is a small speedy back. He can get through small holes that close much easier than Trent (wide back) can. Look at the holes Brown is running through. They are tiny and last for less than a second. He's having to bob and weave and get as small as he can to get through those wholes, and Richardson is physically incapable of making himself that small. I really don't think Richardson is a bust; I just think he isn't getting the holes he needs. This is why I think Brown is more successful than Richardson currently. Not because he's just an all-better back, but rather he's then only back small enough to get through the tiny holes.
I could be completely wrong, feel free to tell me why. I'm just waiting for an email at work so I figured I'd voice my thoughts on here.