Better - Sapphire Plus, with one exception.

X5SA Pro is a bit of a lucky dip. Sometimes you get a good one, and sometimes...not so much. However, if you plan on making significant upgrades to the machine, then the open frame design of the X5SA may make it 'better'.
If you just want a machine that will print with minimal upgrades, then the Sapphire is a better bet.

Aardvark, I'm pretty sure both the OSG rails (TronXY), and the MGN12s are generally considered rails. They are just very different styles. I also doubt there would be any significant differences between the two in usage.