I voted Cena/Batista for a few reasons.
1. The build up is already better for Cena/Batista than Edge/Jericho. It looks like Edge is turning into a John Cena type face with the 'Spear' routine that got old about 3 seconds after it began. They don't even seem to be worrying about the history between Edge and Jericho, it's just been thrown by the wayside.
2. Believe it or not, the match quality is going to be near the same, imo. Edge and Jericho are two of the best workers in the company but Cena and Batista have even more of a personal rivalry brewing. It is already more layered than Edge/Jericho probably will ever get by time for Mania.
3. The atmosphere is going to be spectactular. I know it's the cool thing to boo Cena, to hate Cena, to shit on everything Cena does but that won't be the case at Mania because there is NO WAY Batista will be cheered more than Cena. For the first time in a long time John Cena will have a definitive home field/court/ring (?) advantage.
All in all, Cena/Batista is being built as THE main event whereas Edge/Jericho isn't being looked at as all that important to me at least. In other words the writing and booking is selling Cena/Batista and it's stalling Edge/Jericho.