It's an interesting question. Sort of reminds me of if you had to get sick, which disease would you want, small pox or malaria?
Anyway, I voted for dairy. My reasoning is that the dairy cows are left alive longer. which I don't think is doing them a favor. also when you drive by a ranch the "beef cows" are all outside in the pasture eating grass (usually for 1 to 3 years). While most of the dairy cows are inside and/or in close quarters. The "beef calfs" are left with their mothers and get to hang out with their moms and play with each other. the diary calfs are separated from their moms.
I voted meat but in the way they are BOTH very cruel so it was hard for me to say. Factory farmed sows suffer a lot especially if they are put in pens when they give birth to their piglets. factory farmed birds are also very cruelly treated. So I don't know.