EDLIN? AIEEE!!!!!!!!!
I'll use COPY CON before EDLIN...

Most people around here will disagree with me, but I say if you're building a single-purpose MAME cabinet with no USB controllers, go with DOS. USB, however, is extremely handy. I run Windows solely for USB support, but I was much happier when my cabinet was DOS, and it was more stable and booted much faster. Basically, it felt more like a real arcade machine, whereas people recognize my current cabinet as Windows.
The biggest disadvantages of DOS are: no USB support, very few front-ends for DOS, no hardware stretching, it can be difficult to find DOS drivers for modern hardware, especially sound cards, and memory limitations (EMM386 can't see more than 128 MB of RAM; QEMM will see 256MB). The "no hardware stretching" issue is bigger than it sounds: I spent a good while trying to find the best resolution for each game, as MAME's autoselected resolution was sub-optimal about 20% of the time. Get Scitech Display Doctor for DOS at
http://www.scitechsoft.com/products/ent/free_titles.html; it'll give you many more low-resolution display modes.
The other big disadvantage is that every time you talk about your machine on this board, people will come out of the woodwork to tell you how awful DOS is and that you "need a modern operating system to get the most out of modern hardware". It gets tiresome defending a DOS decision after a while.
--Chris