Actually there's something about the D/A convertors that Akai uses that makes the mpcs have a signature sound of sorts. (Punchy... clean.. etc) That's why some favor the akai sound over emu or vise versa.
Yes, this was definitely true ten or fifteen years ago, on the MPC-60 and early S-series vs. the Emu Emulator series vs. Yamaha samplers vs. Roland vs. Ensoniq, but the MPC2000/MPC2000XL/MPC1000/current stuff all use pretty off-the-shelf parts. I've heard many people talk about the difference in sound, but have yet to meet anyone who's actually A/B'd them who can tell the difference. :)