Resin is pretty good but has its drawbacks. The resin comes out smooth as you said and does not have layer issues. However, most resin is brittle and would crack randomly.
I had some resin props printed the same way with the same resin last 20 sessions and some last 20 minutes. There was no consistency. I have found the tougher resins that cost more do not break but they flex to much and the prop vibrates. It seems to make the resin more durable and less brittle the resin is softer.
I have printed about 15 types of resins and 10 or so fdm filaments including CF varieties and plain polycarbonate has been the best I have found for printing prop blades. I have some that have lasted over 50 hours of run time. They generally don’t break unless you hit an object in the water.
I print the folding prop blade horizontal and rotated so the bolt hole is vertical. I aim the curved side of the blade (leading edge) pointing up and the trailing edge down.
Supports are used but it doesn’t end up supporting much of the blade area. I can wet sand the blade with 180 grit for 5 minutes or so and get a perfect finish.
I feel this is much stronger then printing the blades upright vertically due to the layer lines that can separate.
I get difficulties with Prusa based slicer support under the blade and edge render.
So I got edges not rendering good, see pic.
Then switched to perimeter generator - Classic. It helped with edges, but the support under the side-bottom most critical overhange is too far…
Also it does not do good with the bottom flat overhange - it is almost a bridge.
Overall it is manageable, but the quality low on the bottom of the blade.
