Preparation is where quotes diverge most and where they are described least. Look for what is specified: wash method, how failed coating is removed, what gets filled and sanded, which surfaces are primed and with what.
Coat counts are meaningless without a product. Two coats of a cheap contractor-grade paint will underperform one coat of a premium product over a correct primer, and it will cost you again in four years.
Check what is excluded. Fascia, garage doors, eaves, downspouts, exterior doors and gates are the usual quiet exclusions, and any of them can turn a like-for-like comparison upside down.
Finally, look for the warranty terms in writing rather than a number in a headline. "Five-year warranty" means nothing until you can read what it covers and what voids it.
