The common perception is that YC is very big on pedigree (top schools, serial founders, worked at top companies). They are known for having a prototype (they liked to call it patterns) of what is the ideal founding team.

500startups for example are willing to take more risks on people and look more deeply at the product if it has traction and a business model, even the founding team is unknown / international.

There's a lot of different investment thesis, which all make sense for different reasons.