Originally Posted by
percysmith
First up, I should put a big caveat on which currencies Amex cherry picks on. Dirty floats like RMB/TWD/THB don't get cherry picked. JPY is also cherry picking-free. It's relatively free-float currency such as AUD/GBP/EUR where this happens. So please do not extrapolate your great JPY/USD rate here.
I see no evidence of this. My experience using US-based cards:
1) Amex rates on average are better than Visa.
2) Variance in rates from mid-rate for Amex and Visa since start of 2017 are almost identical. (sd=.0034 vs sd=.0032)
3) Variance for AUD, GBP, EUR and THB are similar. (sd(all currencies)=.0034 vs sd (THB transactions)=.0028)
None of these things would be true if Amex was cherry-picking bad rates when they can. (Unless Visa is cherry-picking worse rates and doing it more often!)
(I don't remember ever using a company in Japan which even accepts Amex, so I'm certainly not including JPY.)
increased by a single conversion commission of 2%
That's a much bigger problem than this one!