Dialga (obviously) uses Roar of Time.
Palkia uses Endure (activates Petaya Berry).
...gets 2 attacks before Dialga can move...
...battle ends.
Yes it's tailored, but all of these 'battles' are anyways. At least this is a new tailored battle.
And as for general battling... Palkia has a single weakness, Dragon. Seriously, that's a relatively rare one - not like Dialga's common Fighting and Ground weaknesses. Ok, so D. can't be poisoned... yahoo, it still gets ripped open by all those Close Combats, Brick Breaks and Earthquakes which Palkia can certainly absorb alot better.
As for looks... buy PBR... watch Palkia spread its wings and move. How can you still say Dialga 'looks' better.
...and them's my two cents.