In reply to Tony the Blade:
Nr 4 gully was favourite for a long while for being easist [tho' sometimes requiring an abseil] and quickest.
Since discovering the 'Bog Trot' from Lochan Meall an-t-Suidhe down to what's known as the Top Car Park, I've switched to that these past few years.
Late last winter, after Tower Ridge we descended the full length [almost] of The Red Burn via the best bumslide ever. The snow was soft. Many others had preceeded us leaving a bumslide version of The Cresta Run - complete with one /one and a half metre deep banked corners!
We arrived right at the Pony Track beyond the steep waterfall crossing of The Red Burn - grinning like Teenagers! [then onto the 'Bog Trot']
Very quick, very exhilarating and very little effort. [A damp ar$e tho' as I'd foolishly omitted to get on the overtrousers].
There's also another gully further 'round East from the Red Burn that is good if coming off The Castle area.
My most classy effort was a solo up Tower Ridge [rock-climbing] - followed by a descent of Tower Gully [down-climbing snow with crampons] then a great swooping standing glissade down - across the top of Tower Scoop and into the lower reaches of Observatory Gully - brilliant but thighs like jelly at the end.