Boolberry is still subject to political squabbles, so it doesn't have the same level of consensus as this thread alone still uses the BBR symbol and the wallets currently also use BBR.
I think BBR is established enough in this community already. Besides, there are too many X** coins around, thus diluting any prestige related to the international standards.Most importantly, though, BBR stands for Bender Bending Rodriguez, a character associated with Zoidberg
XBR has no personality, it was an strategic error. I hate it. Boolberry and BBR both have a very differenciated identity.