Well, anti-aliasing will be slower. (Why use AA if not transparent ?)
And I think compression applies only to JPEG files. (At least this is what the docs say. Yes, I do notice that all 3 code examples have a compression option for a PNG write. Something to ask @tt_su about.)
SketchUp is using a compiled library for this, so I doubt using interpreted Ruby code could be faster.
If the elevation scene pages were setup ahead of time it might be slightly faster but I don’t know as the user would perceive it.
RELATED: Some ideas can be got from:
It should be termed as the “proper option” as send actions are meant for toolbar buttons not code. They are asynchronous, as you found out, and the following code statements run before the file actually gets written. (Likely the 4 files look like the final “right” view.)