FFX version of each?
Lulu would win
I mean in the assault of the wedding scene, she is also grinding on the iron chains with tidus and auron and gang.

Lulu was also a guardian 3 times over, meaning she definitely has the battle experience, even if it's for the magic, she can still think better.

Lulu also has the attitude. Yunas attitude was too cute in FFX to be taken seriously

FFX-2 versioin
Yuna is seen doing a weird dismount in the beginning meaning she has learnt some new moves haha
And lulu is pregnant sooo... No contest

Lulu wins in the first,
Yna in the second.