I don't have mine yet, I pick it up tomorrow woohoo!
Off just research of why I chose it, the Saker has flexibility. I can use direct thread or QD and the ASR seems to have good lockup. That being said, I do like the Keymo's ease, but after asking about the lock ring of ASR the people that have and run them eased my thinking. I can always just get a direct thread and use it if desired and switch whenever.
I was using just published numbers, but it seems suppression for the 308 is pretty good. Mine will be on semis so that was another deciding factor. I'm hoping it does well on my rifles that are 6.5 Grendel, 6mm Creedmoor and 6.5 Creedmoor.
Can't comment on 300 Blackout. I don't have one and don't plan on getting one. The big bore that I have is a 458 Socom so I'm the not to distant future I'll be looking for a can just for that.
I'll be getting it out to see how it does for me as soon as I can and will post some impressions. You mentioned long and heavy, the common info on that is that it is a tank and is durable because of it. Another plus in my list of wants. I did a lot of looking and that's why I decided to go with a Saker 762.