hey,
i run a small 8 track studio, i run a Mac Book 2hz dual core, Logic Studio 8, with a usb interface the Edirol - Ua101, with a behringer Xenyx desk with 8 mono signals out.
This is enough to record proffessional sounding demos and making complete albums, and in my experiance from using friends DMR's ive found my system ALOT more versatile. With DMR's you have to go through alot of arsy menus to find what you want, with logic or even cubase, its right there on a nice big screen for you to just click away.
But saying that, at uni we use Radar, which is a more classic way of recording and mixing, it has 24 track simultanious recording, and 24 track play back channels. This is VERY expensive however lol and you will need alot of outboard gates and compressors and effects etc.
although a good way from getting a system with a computer and a mixing desk, would be a USB mixer, you can pick up an 8 track in/out usb mixer for around $500. You would use Cubase as a means of recording with one of these or any other audio program.
so yeah, in my personal opinion i'd go for PC/MAC, its alot cheaper to run it, and has alot more capabilities if you have the right plugins
hope i helped :P
Tim