The f801 is a darn good camera apart from the weight which makes it a feel like a solid chunk of plastic brick, it is fast and accurate i usually keep it underneath my car with a kit lens for spontaneous street shots which can happen anytime of the day. I do have an FM too in a user condition, thinking of repainting it. M6 is different as it is smaller lighter and more compact, however, it may be practically viewed or feel as a 'luxury' camera instead of a tool camera that can survive in any harsh condition.
Btw, most films i use are ASA 400 namely the kodak triX, ilford delta 400, Pan 400 and sometimes lucky films pushed to ASA 400.