: I just spent the day sanding my deck, and was thinking about the same thing
: as Steve. What looks best in the end: filling with wood filler, filling
: with sawdust and epoxy, or just letting them fill with epoxy by
: themselves?

Filling with sawdust and epoxy always produces a darker color than the adjacent wood, which draws the eye to the defect. Sometimes you can get lighter sawdust from other wood, or add a whitening agent (e.g. flour), but proportioning these is tricky. Oil-based wood fillers are to be avoided too, they will stain the area around the fill. So IMO the best way is water-based wood filler, which can be adjusted to match the surrounding wood. Try it first on some scraps or a mockup, it's easier to do it than to describe it.