Either penetrating or film forming and each has its pros and cons.
Best finish for front door.
Exterior paints are sold in flat matte eggshell satin semi gloss and gloss sheens in order of the lowest to the highest.
Go for a semi gloss finish which is as durable as it is attractive.
Most door companies apply a paint or poly finish before delivery or you can save a few bucks by ordering the door unfinished and coating it yourself.
While you can choose any finish glossy paints are typically preferred for doors and trim because they stand out and highlight these architectural features.
Clear oil finishes come in two basic flavors.
The combination has worked amazingly well for me on a west facing exterior oak door that looks as good today as it did after refinishing 7 8 years ago.
The best clear finish for an exterior door is 3 coats of clear epoxy followed with 2 3 coats of spar varnish.
For use on an exterior door waterborne finishes are getting better but oil finishes still rule.
They also tend to stand up to nicks and scrapes better than flat or eggshell paint meaning they could last longer.
Just be sure to seal all edges so that the wood doesn t wick up moisture.
The same goes for exterior trim.
Types of clear finishes.
No other clear finish matches its durability and moisture resistance.
Penetrating oils are beautiful and easy to maintain but they aren t as durable as film forming coatings.