Doug Miller wrote:

In two ways: first, I'm still using the same PIN, too, so I didn't have
to memorize a new one.

Good point, although my credit union will put any PIN on the card I want.

Mostly, though, the benefit I perceive is that
it's not possible for me to accidentally debit a major purchase from my
checking account, instead of charging it on MC like I meant to, simply
by inadvertently pulling the wrong card out of my wallet.

I know that feeling! G

I have a company charge card that allows no personal use. I keep the
three cards in my wallet in different colored Tyvek envelopes. On
occasion, my wife uses my wallet online 'cause I leave it next to the
computer and her purse is elsewhere. Twice she's put the cards back in
the wrong sleeves and I've had the company card out for major purchases
and realized what I was about to do.