The pros are:
More connections in a smaller space, the biggest plus and the main reason I would think.
Quicker disconnect, each d-sub is the same as 8 XLR's
Con's:
Soldering the bloody connections, 24 in each d-sub.
Carrying spare cables is more costly.
Can't think of any other reasons?
Alan.
p.s.
Missed the question about the snake, a snake is any cable that carries multiple channel of audio over a distance, can have jacks, xlr's d-subs, video, or a combination of all of them.