Bitcoin paying signature campaigns take a very few members in their campaign, so you can't join in those campaigns anytime! Everybody loves bitcoin paying signature campaign because most of the BTC paying campaigns are pay bounty rewards on a weekly basis! So, Hunter can sell or trade immediately, no need wait for an exchange. And only lucky bounty hunters can participate in BTC paying signature campaigns nowadays. So, Have a try if you get one.
But today the number of bitcoin paying signature campaign has reduced and stagnant. While the number of ICO bounties never stops increasing its number day by day. Every single day there's new one but there's no assurance with them.
Unlike the bitcoin paying one, you'll get assured if the manager is well trusted and popular to secure funds while the ICO one will only distribute your rewards after their ICO.