Mac 6500 4ohm vs Mac 6900 driving 8 ohm speakers

Driving a Mcintosh 6500 at 4ohms will output 200 wpc.
Driving a Mcintosh 6900 at 4ohms will output 200 wpc.
So that being said. will they be indistinguisable in audio quality? Would you be able to blind test a difference in the two amps using say magnapan speakers?

Thanks in advance for insight
The MA6900 has autoformers while the MA6500 does not. Some people swear by the Mac SS amps with autoformers as the Holy Grail. But I've read that direct comparisons between these two hasn't reflected much of a difference. I guess it all depends on your budget and whether you can listen to both. It also might depend on your speakers and whether you're really going to push them hard. That said, I've read that they are both excellent.