How to choose profitable bounty ? What factors we should analyse before pick any bounty 
I will try to help you:
1) the First is bounty Manager
2) Who in the table is in category the signature, if there is a hero or legendary, you should enter
3) try to find companies with less than 1000 members (TWITTER Facebook)
Perhaps these are the main criteria that I use.
Nowadays is it very difficult to find bounties with less participants than 1000. So I think that it is better to participate in both Twitter and Facebook bounties, to get from two different pools an allocation. Otherwise are the earnings less.