I have an older qnap that is running xpenology. I agree QNAP traditionally has had stronger hardware in their boxes (why I went with them over synology the last time), but the SW side is lacking. They have been playing catch-up in many areas to synology in their OS, and their mobile apps (especially for apple) are limited compared to Synology.
I guess it really comes down to how you are going to use it. Great transcoding, but if their mobile app is lacking, what are you going to play it on???
One thing to note, I have seem many on the qnap forums getting the x53 families up to 16GB of memory (even though qnap/intel only say 8GB). While it is "unsupported" there are several posts about it working.