I'm not sure most of us could tell the difference between RES and (CN)BG at an inch length; I know I would not have any certainty to such a decision I made personally.
This is a small (1.5" - 2") BG:

and I
think this similarly-sized Lepomis is a RES:

Note the differences in the side patterns (stripes vs. dots). None of the experts (Bill Cody, et al. ) contradicted me in this assessment in a recent thread on small Lepomis I.D. (which I couldn't find just now, or I'd link to it), so I may be right.
In my pond, the RES do not develop the little red ear tab until they are nearly 3" in length.