It's more of a convenience factor and cost I think assuming you can buy an OTA for the 211z. But think of it like this as well, it's almost like integrated versus a modular design so if the OTA failed on the previous 211s, you have to replace the entire receiver but with the 211Z, you just change the OTA part of it and still use the same existing 211Z. Similar to a Receiver which is the Tuner, Preamp and Amp but the later is usually better and you can change that individual portion instead of the everything.