Now, there are 2 kinds of noise to deal with:
1. Environemental noise. This is everything around you, plus the sound the laptop makes (fans/HDs/etc).
2. INSIDE electrical noise. On my old Insprion 7000, I used a reg headset (stereo/mic plugs). I couldn't use Dragon because, according to some techs I talked to, the laptop's wiring wasn't properly shielded and lots of interference was getting through. Any recording had lots of electrical hissing and buzzing that WASN'T around me/in the room.
I bought an inexpensive USB headset, and the sound difference was like night and day. So, I wouldn't base a laptop decision on dictation software needs. Both/either will work, but you probably will need a USB mic/headset to get the best results.