Anybody know if Jhin has more AD mid-late game with AS reds and quints or AD reds and quints?

The difference is so small it's not worth an additional rune page. Just bring the standard page.

Short answer: AD runes > AS runes in pretty much any case.

Math: According to Jhin's passive, 1% bonus Attack Speed = 0.25% multplier for AD.

1 AD red = 0.95 AD 1 AS red = 1.7% AS = 0.425% bonus AD

For that to break even, you would need Actual AD (before other multipliers from his passive) * 0.425% > 0.95, which happens when you have 224 AD. In reality, you would need even more than this, since the 0.95 AD from the runes would get multiplied by the other bonuses on his passive. This math does not change regardless of how many reds you take.

Similarly for quints

1 AD quint = 2.25 AD 1 AS quint = 4.25% AS = 1.0625% bonus AD

AD > 2.25 / 1.0625% = 212 AD

As with reds, the number of quints does not affect this result.

So AD runes > AS runes in pretty much any case. You might be able to build straight AD with no crit or AS and get a case where this works out in the AS rune's favor, but with a standard build that will get 50%+ crit and 30%+ AS from items, the AS runes don't stand a chance.