Touch ID speed variance/issues?

The more fingers you register, the slower the unlock. And if you register the same finger twice it just confuses touchid and can slow things down.

Remove all but one finger from your slower phone and see if that speeds up your unlocks.

Also, we're the phones setup from new or restored from a backup. Try resetting all settings and see if it's still slow. Don't worry, you won't loose any apps or data.

 

When I first got mine, it was slower, but now has sped up. Apple says it gets to know you as you go. Also, I've found that it has a harder time if your fingers have more oils on them (not saying you have dirty hands, it's just natural for some people to have more oily skin than others). My skin tends to be a little more oily than my friend, so it sometimes has a harder time recognizing my finger vs him on his. That's the nature of fingerprints.

It's not just iPhone, when I go to a fingerprint scanner coming back into the country the Global Entry kiosk takes an extra second and sometimes asks me to reposition my palm on the fingerprint scanner because it can't get a perfect read.... completely normal.

 

There are also certain finger positions on my 5s where the phone will unlock ridiculously quickly and others that are a tad slower.