If YC isn't exclusive enough for you, I'm sure you can find a more exclusive accelerator.
In the eyes of customers, I don't think it would give you an "easier time standing out when competing", but I guess everyone is entitled to place their own bets.
Not in the eyes of customers, but in the eyes of future investors. I don't think customers should know or care what accelerator a company went through, although Cinder does advertise itself as "YC-backed" in order to convince customers that it's not a Kickstarter scam.
In the eyes of customers, I don't think it would give you an "easier time standing out when competing", but I guess everyone is entitled to place their own bets.