I think the better one is the signature campaign and it will target the real users. When it comes to bounty campaigns, anyone who can create multiple accounts can participate. So this is not good for the project long run.
This is where all sorts of problems lie when choosing a specific solution. If we choose a signature campaign, we minimize the use of bots, but we reduce the spread of the project, the number of participants involved and increase the budget. Large-scale campaigns are very expensive. If we choose a bounty, we increase the risk of bots, but the budget decreases and the spread of the project increases. The golden mean is extremely difficult to find, especially if you have limited resources for the campaign.