I was out for a hike to Phantom Ranch (1 night) and back the next day second week of January. Park Rangers adviced me the "classic" loop: down South Kaibab Trail (SKT), up Bright Angel Trail (BAT). Some reasons for that:
1. views, views, views...SKT definitely has the best views of the Canyon and those are best enjoyed while descending, 2. SKT of course is steeper, so most people (not all!) would prefer going down the steeper trail and 3. SKT has no water or shade (consideration in summer); both needed most during the ascend.
The trail is in absolutely perfect condition. The first 1/2 mile were snow covered (not really icy) and very well accessible with my rugged hiking/mountaineering boots. I bought YakTrax at the bookstore that made hiking on the snow very comfortable (worth the $25). Rest of the trail is just plain easy to hike down. I arrived at Phantom Ranch (7.5 miles, 3800ft elevation difference) exactly 3 hrs after my start. I did not take breaks besides taking some pictures.
The trail is 7,5 mile with an average 16% grade (to put things in perspective: the Upper Yosemite Falls hike, for those who've done it, is over 22% following the much rougher 4 mile trail)
See my review of Phantom Ranch for my thoughts on (staying at) the bottom of the Canyon, if interested.
I doubted extensively taking SKT back up or BAT. I decided to follow the rangers advice and complete the loop using BAT, despite it being 3 miles longer. It certainly was a good choice. BAT is a totally different trail, wider and easier, but also very nice. During winter the trail is just empty and the solitude was just great! Last 3 miles were snow covered and little slippery. I would have managed without, but was very happy wearing my YakTrax again. They are like airconditioning in summer, you can manage without, but once used to it, you don't want to!
I hiked up to the Rim in 5 hours, taking two 15 minutes breaks (at Indian Gardens and 3-mile house). Nutrition (fix and fluid) and consistent pace are the key words. In summer heat is the enemy, in winter...there was none, not the snow, not the record cold (20F at noon at the Rim!) and not the fresh now. Did only the Plateau Point loop in summer once and it "killed" me, now I know it was the heat *only*, that made it a struggle.
Would do this hike again anytime....but summer: dangerously hot and way to crowded!!