We are a complementary middle ground between upfront grants and retro PGF. 
Upfront grants prioritizes builder security because the builders already have funds. However, funders have no guarantees.
RetroPGF such as Optimism’s is great for funders who award based on the impact seen of a project. However, builders have no idea if or how much they will receive.
With crowdfunded prizes, builders know how much funding is available for a specific scope of work and funders have guarantees that it will either be built or they will be refunded. 
These are all helpful in different ways, and we would love to see a future where projects receive all three (potentially starting with grants before building and ongoing, then prizes at the time of finishing building, then retro PGF at the time of impact)