It's a tough call, really, but I don't think there are a lot of budget pres out there that are noticeably better than the mackie, to be honest.
I think the dmp3 really shines when recording very quiet sources. You can crank the gain up on it well past 12 o'clock without the sound changing noticeably, if at all. Not to mention it's probably about the quietest pre in it's price range, hands-down, so I'd say for mic'ing quiet things (very soft voices, classical guitar, etc.). This also makes it pretty ideal for quieter models like ribbon mics.
The mackie, on the other hand, doesn't maintain a very flat freq. response when you push it to higher gains, and although it's still impressively quiet (all things considering), it's not the same as the dmp3.
On the other hand . . . if you're mic'ing louder sources, the mackie might have a very slight edge in terms of headroom (and possibly it's lower distortion figures). This was much more of an issue with the dmp2, but still could with the dmp3 under extreme circumstances (in which case you should probably back the mic off or use a pad anyway).