I dont really consider either to be a real true amiga right now. But i would say the AmigaOne with AOS4 wil be more of an amiga that pegasos, only because of its official partnerships and branding. Mind you i wouldnt mind running AOS4+ on whichever is the better board based on my personal requirements in future, performance vs cost vs size. Yes smaller is better to me as i can do far cooler cases and dont need more than 1 or 2 pci slots.
I think people opinions will change when AOS4 comes out and runs on many hardware configurations, and this question will become as ambiguous as "Do you consider either the ASUS's or GIGBYTE's to be true PC's?"
Speaking of which, one thing amiga should consider in my opinion (and some others ive spoken to as well) is porting aos to x86 but only support a small group of boards and chipsets, eg certain ASUS or GIGABYTE models. This would get the prices down, the performance up, fix supply problems and solve the compatability problems with the multitude of PC hardware configs out there (as amiga would only support a few of the best and most reliable ones) They have already apparently made the OS mostly hardware independant now apart from a small group of functions... I wonder why...