There was something he said about the standard ECU suffering from a 'cough' under certain conditions which is widely acknowledged, which could result in engine damage. That's why he went Omex 710. The Omex loom is tied into the standard ECU so dashboard works normally.
standalone also gives you many extra functions over std, launch control, anti lag, flat foot shift etc. I guess it all depends on what you want.
Recently mapped and dyno'd at 480 bhp on high boost (1.9 bar)