Brother, I share your addiction. I have too many lenses too. Moreover, I recognise this fact and almost certainly will acquire more. I suppose it's due to a misplaced expression of the instinctual hunter-gatherer instinct. It's what brought you here. You know as well as I do that there's not much point in watching this video, let alone making it. But here it is. The A is more automatic; it cooperates more readily with modern cameras. The M will give you more issues. I couldn't use it for video on my K1. The optical difference between them is minimal; the intermittent sun made a much greater impact. Sample variation is also an often overlooked factor. As it turns out, the Pentax 50mm f1.7 M which I sold for £15.30 - or less than $20 - was the better lens. I was quite surprised by how good it was actually. Anyway, you can judge for yourself; I've uploaded comparison photos in high resolution for you here;
https://www.flickr.com/photos/1478587...
https://www.flickr.com/photos/1478587...
https://www.flickr.com/photos/1478587...
https://www.flickr.com/photos/1478587...
https://www.flickr.com/photos/1478587...
https://www.flickr.com/photos/1478587...