I think both satin and gloss would be good, but I prefer matching the front bumper spoiler and rear trunk spoiler (e.g., 1LE). That said, p47dman's car, pictured above, would be an exception (in my eyes) because it looks great and still has an overall good continuity (plus CFM looks great against WCT).
My car has a gloss (1LE) trunk spoiler in CFM; although, I don't have great pics of it, see here:
https://www.camaro6.com/forums/showthread.php?t=627876.
I picked up an OEM '16-18 1LE front bumper spoiler (in primer) because I prefer it's look on the LT front fascia. I'm getting it painted CFM to match my rear spoiler.
However, the satin finish will likely be lower maintenance, and
might stay looking good for a longer period of time.