As far as I know it is the same exact curve, just slowed down.

I don't know what the "best" curve is, particularly assuming they are just time-scaled versions of each other. If slower is better, then wouldn't something even slower than BBR be even better?

I argued for a slower XMR curve early on. I did not prevail.

Although I lost the debate over the XMR emission curve, I wasn't sure the chosen curve was a bad one. (If I were sure enough, I would have dropped out of the project at the time.) I think it mostly depends on rate of uptake. You don't want all the coins mined out before there is adoption (and significant increase in coin price) because: 1) it means mining rewards will be too low to adequately secure the network, and 2) it encourages forking (ie. why XMR was forked from BCN: BCN was 82% mined with virtually no adoption).

XMR is approximately twice as fast as Bitcoin. It seems that given the greatly increased maturity of the cryptocoin concept, it is plausible to believe that a successful coin could uptake twice as fast as Bitcoin now. But I don't really know.