Sandyut, not the original poster but I have my Yoder YS640 now for just over three years and was the best decision I made. I spent nine months dragging my wife around trying to decide on an offset and a Stumps until I saw a Yoder. Hands down I decided I wanted the Yoder, took six more months until I had the money to order one but glad I did. The problems I had in the beginning were user related and customer support from Yoder was fantastic. Not sure about the other manufactures but I was really impressed when I had received emails and a call from Don Cary, who owns Yoder, to provide assistance.
I have no garage so mine sits out in the elements year round on my deck, I also smoke all year round. Rain, snow, ice, wind, etc doesn't stop me. I have not had any problems with burn back in the hopper or it not igniting. I keep a spare igniter and thermocouple and fuse just in case. When Yoder upgraded the fire grate I bought the upgrade. When they upgraded the deflector plate to a two piece on, I bought it. I keep the thermal jacket on it year round and after 2.5 years I took it off for the first time to inspect for rust, there were a few dime and quarter size spots but that was all I had. Others were posting on the Facebook Yoder fan site that they were seeing a lot of rust. Almost all of these people were using the Yoder cover. I have never used their cover, and will only buy covers from The Cover Store and only use their Ultima covers. They have venting in them that seems to help with keeping off moisture.
The one thing that I do is dump the ash from the fire grate after each smoke. with the two piece diffuser all I do is pull two of the grates, lift the trap door, dump the grate, wipe off the igniter and thermocouple and put it back together, usually in less than five minutes. After a few smokes I'll pull all of the grates and diffuser plate and vacuum the inside. The two piece diffuser plate is a must, before that lifting the one piece as a bit*h, it was heavy. Turning 61 soon and with a bad back, it makes all the difference for me when smoking.
Hope this helps in your decision