I have both, and the corded has always been my favorite, simply for longer use and massively more torque.
That being said, last week my 4000 stopped working abruptly. Shut it off, would not turn back on. I was in the middle of a project that couldn't wait, so knowing I would have to send the 4000 in for repair, and not seeing a good reason to have TWO corded one, I purchased the 8200. Last night, it quit as well.
Not very happy at this point, $200 on tools, who knows how much in accessories (I go through cutting wheels like its nothing). My Black and Decker rotory tool cost half as much and ran well for a very long time.
There is a learning curve. My 8000 cordless has been great, but the first time I was using it with a low battery and it shutdown, I was sure it was broken.
Nope! Turn it off, wait a few seconds, and go back to work. I have two batteries so I usually change batteries when this happens. Otherwise, it will continue to shut down under relatively light loads every few minutes. Not fun!
Anyway, charge up your 8200 and you may discover it is not broken after all. Here's hoping!