It depends if you are looking at the niche as a quick win or a long term investment.
Quick win - go CPA. Initial deposit levels are usually low.
Long term - go rev share as bingo players are slow burners. Slow burners will chip in to your monthly cheques every month 'forever'. The more players you get each chipping in a small amount, and eventually you will make decent money.
HOWEVER its a very crowded market both from a brand and affiliate side. The brands have either been around so long that all the players already have an account (so all you do is restart existing affiliates tagged players - as a long standing bingo affliliate I'm cool with thatbut you might not be!) or they are new, 'metoo' brands that offer nothing new and only attract bonus hunters.
There are also a number of large, very successful affiliates who have been in this space a very long time, along with newer ones (some of whom stoop to
very black hat, naughty stuff.). Unless you are serious about this niche you will probably find you get more money for your effort sticking with what you know.