I got rid of all but two of my x86 machines which didn't have AES-NI. One is essentially unused, and the other is my current home theater box, to be replaced with the Late-2013 Mac Mini. AES-NI essentially makes Full Disk Encryption "free", and FDE is a minimum standard for any machine I'd use today.

If iOS gets biometrics, I'd probably feel the same way about it (and fixing the imaging attack is why I upgraded ASAP off the iPhone 4 and iPad 1). If Mac hardware added real trusted boot hardware, I'd probably replace all of mine at the same time, too.

So, not performance, but features.