Prob pork, because it's cheaper. Beef ribs are expensive as fuck, like $6 per rib, while a rack of pork ribs costs like $2-3 per lb, or around $10 per rack.
I went to this place that sells meats to restaurants, and a 2 pack of beef ribs, like 6 total ribs, was like $40. Now obviously it was bigger, but even by lb, I think it was $5-7 per lb, while pork ribs were I believe $2.25 a lb or something.