Both has its own plus and minus. Most cases in here, bounty started before its fundraising. Kinda rare to find a bounty while fundraising is ongoing. But sometime there's a bounty that finished their private sale. Whichever you choose to, anything could happen at the end of the day. If you're joining a bounty before the fund raising, you won't know if it will succeed or not, and in the middle of fund raising you could see how many investors are in there to invest their money. With all that in mind, you could know how well the projects will be.