My experience with Langley is a bit different than Snacking Bear's.
First, with one exception, I've always done it via Army Pass (sometimes called Old Army to differentiate it via from New Army). That pass does require a longer wait in the spring/summer in order to melt out as it has a sheltered exposure. So, while the snow generally melts in most sections much earlier than Whitney due to different exposures, the bottleneck on Langley is usually these Army Passes. New Army tends to melt earlier, and if there's no cornice (a seasonal variation due to winds during any given storm) is safer to navigate while snow-covered. The New Army route is a bit longer, and does require a slight loss/gain of elevation.
Whereas Whitney has mostly continuous grades, Langley has long sections of either mostly flat or slightly uphill sections, so with the exception of Army Pass (which only takes about 30-45 minutes to do) you have a much easier time of it than Whitney, with the exception of the soft sand/scree which he describes near the top 1/2 mile or so. The starting elevation at Horseshoe Meadows is 10K, so the overall gain is a bit over 4K over approximately the same distance.
There is a different "feel" to Langley as well - there are several lakes on this route, with walks thru at least one meadow with a large marmot population, and a good chance of seeing bighorn sheep up high. If you pass by the last lake on the descent near dusk you'll almost certainly see lots of deer.
So, do I prefer one over the other? No, they're both great hikes, just different. And, you won't need a permit to do Langley unless you're planning an overnight.
