Rates are the same whether written with the NFIP or a WYO company.
Recently, more companies, like Lloyds of London, have entered the flood insurance market and developed their own rates, which are often lower than NFIP rates. These policies are not federally reinsured.
Flood rates depend on
the type of policy - residential, condominium, business
the flood zone in which the property is located
the elevation of the building - if it is in a special flood hazard area (A,V), a flood elevation certificate, prepared by a licensed professional, may be required.
the number of stories of the structure and whether there is a basement (below ground level on 4 sides).
Properties in zones B,C and X qualify for the Preferred Risk Program
There is a 30 day waiting period
for new policies to go into effect (there are a few exceptions). It's too late to buy flood insurance when the hurricane or flood crest is on the way.