Well that does up the ante when it comes to tourneys when people use shadow characters for the extra health.
So say, I go as Junpei and I fight a shadow yosuke, he has more health than his normal glass cannon-y self.
Or if I use shadow kanji against a normal yukiko, I got the extra health buff to take more damage from her agi, combos, and fans, etc.etc.
It's like this situation wise, but there are possible work arounds in done right. This does give the shadows a better chance in battle due to the lack of a burst