There is no time either of them can reduce the fee you are going to pay. Static, eta and mempool are just Electrum's algorithms to estimate fees for their users, so it depends on the one you wish to use. Eta and mempool options are better because they estimate based on market conditions, while static is just fixed and you simply select from 1-300 sat/vbyte. However, the best method is still to check mempool.space before setting your fee rate or manually inputing it if you use Electrum on desktop.