1. Payout structure (PPS+, FPPS, etc.)
2. How much of the hashrate the pool controls
3. Withdrawal limits & options
4. Policies and Legal constraints (e.g. KYC)
5. Protocol support & operational support (e.g. stratum V2 support, dashboards)

There are several points of differentiation pool operators can use to make a compelling offering for miners. It comes down to what sort of trade offs you want to make as a miner.