Xeon selling point over i7 is fact that you can link 2 on same board. By switching to a single CPU only Apple has gotten rid of that justification for not using i7 CPUs, especially for cheaper models.
i7 do not support ECC ram.
i7 have less cache than Xeons. A lot less.
Even with PCIe based flash storage, it is better to have a large, fast, on die cache than a smaller one for most computing.
Frankly Apple stuff usually is a tad behind the latest tech.
But the build quality is excellent. Every year we recycle dozens of old computers at my job. We get rid of everything that is 4 years old, as is the standard in most large businesses.
Its a pretty good lesson that the PC's going out the door are thrashed and almost unusable. The Macs, especially the Mac Pros are still perfectly viable computers.
I'm a computer hardware tweaker so you would think I'd have a hackintosh. I certainly have the parts if I cared to build one. But for me at least it defeats the value of a Mac to me.
I like my Apple products to be appliances. Turn them on and they work. I do not want to have to chase down any conflicts or glitches. I don't want to worry about thermal management.
I do that all day long at work.
My work Mac, studio Mac and home Mac are all suited to their tasks and carry them off with reliability (10.8.5 notwithstanding!).
If I want to play with computer hardware for fun I'll build a windows PC for gaming on.
The real zinger to me though is that any hackintosh is one Apple update away from being bricked.
At some point they can just insert a piece of code that further closes the already pretty closed ecosystem and it may render not only your OS non-functional, but I wouldn't bet money that any App store purchases would be honored. Not for that machine at least.
Apple is inexorably moving to not just a walled garden, but a domed garden that you can't even water the plants in. If you want the Apple curated experience buy a Mac. If you are just testing the waters or super broke go for a hackintosh. But I think it is a fools errand to build a "turbo" mac from off the shelf parts for a production machine.