Easier access to assault/defender weapons. Light is known for having a shit ton of them.
*sigh* Didn't mean to drop a fking bomb. That's obviously just a l'art pour l'art thing with hp in center. No need to overthink it.
I already got ~8k base hp on light team with no FLB, 2 0* hime weapon, 1* Phoenix bow & 2* 2nd Nicholai sword + only half of my grid being +99. You can go beyond 10k with ease if you're a freakin' whale. And also forgot to consider the premium eidolons that got way higher hp stat most of the time than event ones (not to mention possible kaiser grid).
Oh, and final note: 5 accessory slot for light is impossible even currently, as still no high rag for light.. and this pic was taken before those rags were implemented, anyway.