GLOCK 20 or 21 for Backpacking?

So im adding a glock to the collection....However, im not sure which model....Here's some info that might help....I will be backpacking with this gun, so I'm pretty set on either a 10mm or 45....If im not wrong that narrows it down (for full size which I want) to the G20 and G21. Are these models both reliable? I always hear about GlOCK having amazing reliability, but was curious if there are any models to avoid? Thanks.