I watched a few of my RES eat pellets today in my RES/SMB pond. Compared to BG feeding they are very selective and particular. Of course part of that could be difference in competition. In my main pond there are lots of BG and intense competition to get a pellet. In my RES/SMB pond there is much less competition and with pellets floating on the surface they have more time to be choosy. But the RES definitely have different mannerisms than BG.
I also kept a few in an aquarium for a while. When I was trying to get them pellet trained they would be interested in the sinking starter feed as long as it was sinking or in some way moving, but would quickly loose interest once the pellet hit bottom. It seemed like they wanted movement before they considered it a food item. I put tiny live snails in and as a snail would move the small RES would race towards it, stop, and stare at it. If the snail moved again they would eat it. It is like it had to be moving before they wanted it.
In my RES/SMB pond I only see a few of the RES have gotten used to pellets and eat them (at least while I am observing - others may eat them after they sink or when I leave). A lot higher portion of the SMB seem to go after the pellets but even they are more active right when the pellets hit the surface.
RES information and links to other RES threads 
