For me, on how to choose a bounty is this on the list:

1.) Good bounty manager, do a back ground check on the bounty manager.
2.) What is the bounty for, know the project well.
3.) If there are some higher rank people interested in it.
4.) If there are a lot of people are interested in it.
5.) And last know who are the sponsors if they have one.

this is only my opinion. This is how I choose my bounties. So it's up to you.