I have one of each. Same functionality, however with the 211K have you more options on which type of remote will control the receiver. When I lost my remote for the 211 Dish sent me three remotes that they claimed would work. They would with the 211K but not the 211. Only remote that I could get to work was the model 5.4 IR.
Given that remotes do get lost, break, etc. I would go with the 211K.
indeed, i have a 211 and I can use the same 21.0 that i use on my 622 to work just fine with it. may want to make sure if you have a toggle switch inside the battery door, that it's switched to IR as well