Sorry, another food question!!

So i know a few people feed one food for both rabbits and guinea pigs.
My question is, which food is the best to feed to both? Rabbit food or Guinea pig food?

Iv rang heygates, who make a 'pet pellet' and Im hoping I can easily get that close by..but if not Im wondering what my other choices are...

Neither is good as an all rounder. GPs need the extra vitamins provided by their pellets but they are generally too rich for rabbits. Rabbit pellets will not cover the GPs needs adequately. I would be highly suspicious of any food claiming to meet the needs of both.