Or, it could be the rare implementation of Remote Play. With a sufficient wireless connection, players can play the game with the PSP system from anywhere in the world. This is one of the few retail titles to take advantage of the feature, the first being Lair (ugh).
Perhaps players are taking advantage of the lack of region coding on the PS3 version. Without a European release in sight, some may look towards importing the American PS3 release. (The Xbox 360 version is region locked.)
However, according to an Aksys representative, the main reason BlazBlue is more popular among PS3 owners is its popularity with Japanese gamers. Aksys' Harry Chang explained that many hardcore players want to play against Japanese players, and people know that the "Japanese players are mostly on PS3." Those that are seeking competition from Japan's best players know which version to choose. No wonder PS3 is Capcom's "platform of choice" at the EVO Championship Series.