Why restrict yourself to these options, when there are so many others? A little Googling will find you many more, although not many with public transport options.

However, Jin Shan Ling is perfectly satisfying by itself, with more romantic unrestored sections easily reachable across a heavily restored section. There's nothing to stop you walking part of the way to Simatai and turning back. And, of course, the Wall does go in two directions, so you could walk the other way towards Gu Bei Kou or start there and walk towards Jin Shan Ling. This route does involved dismounting for a while as there's a military base on the interior side of the Wall about halfway between the two points.

The last time I walked from Gu Bei Kou to Jin Shan Ling I didn't encounter anyone else at all between those two points, save a few farmers working in their fields.

The priced-for-tourists bus tours don't go anywhere very interesting and are amongst the most expensive ways to get anywhere anyway, so should be avoided. Chinese bus tours departing from Xuanwu Men at weekends are very good value, however, but their Great Wall destinations are limited to Badaling, Juyong Guan (not a bad choice, but the closest officially open section of Great Wall to Beijing, although visitors there are a fraction of the numbers at the most popular sites), and Huang Hua Cheng--but not the 'next big thing' Huang Hua Cheng you may hear of (and which its officially forbidden to climb, not that anyone takes any notice), but a neighbouring section partially submerged by a dam, with rowing boats for hire, etc. etc., and best avoided. There used to be bus tours to Jin Shan Ling, but not recently, although it's worth checking to see whether they have been revived.

Mutianyu can be reached by public bus 936 from Dong Zhi Men Wai, and Gu Bei Kou (Panlong Shan) and Jin Shan Ling by long-distance bus to Chengde, simply jumping off at the turnings, leaving you with about 45mins to the base of the wall at Jin Shan Ling, and maybe 20 mins at Panlong Shan, although there are often farm vehicles around that will take you for a small fee.

Peter N-H
China