I used an 850 for years. I am currently using the Clarity aloft.
Personally I prefer the 850. It is quiet enough, light enough, durable, and reliable.
The clarity is comfortable after some break in time. It is very light weight. After a year of use, I continue to dislike the earplug aspect. They never seal perfectly in my ears, they get dirty from your body and the surrounding environment, and the earplugs seem to "disappear" at the worst times. They just fall off (easily get pulled off) when moving the headset around. So you must keep extras on hand at all times.
Seven years of 850 use and all I had to do was replace the ear pads and mike muff. I was pretty rough on it, and it held together perfectly.
One year of CA use and I have had to send it in due to total microphone failure. I've replaced the ear plugs many many times. I have to throw in that clarity aloft's customer service is excellent.
Friends have also had mic failures and ear plug sound failures. Again, CA is used to it, and will send you another one fast.
Some love the clarity and it is an ok, unique product that works well when it works. For me I'll be switching back to the 850 soon.