[JasPR]

that logic wouldn't boded well for feeding whole shrimp then! Koi do not digest and assimilate food the same way people do for two simple reasons:
1) they do not have stomachs ( long digestion guts many times the length of the actual koi)
2) they are cold blooded and assimilate is regulated by temperature.
If you are suggesting that the heavier the meal, the more fish will absorb, this is not correct as any sump will tell you- and your nose. It is the assimilation rate ( and movement of food through gut based on temperatures) and not the pounds per inch that are packed in during a single feeding. This is why auto-feeders are used or why it is recommended that fish be fed small meals several times a day in growth season as opposed to large single meals.
So in the case of the same formula pellets, the assimilation rates of two size pellets would be the same ( assuming same temperature) but limited by the ability of the gut to absorb ( the old eye bigger than the stomach issue) total calorie intake in a given time interval. If you are suggesting they would be able to take in more pellets per minute- then you are suggesting a limited amount of pellets being offered in a limited time interval ? 5 minutes of feeding and most koi will be content. Once you cross the line of the actual absorption rate, you get things like white stools ( fish diarrhea). This is called the ‘digestion energy rate, which refers to the feeding response AFTER the first two or three means of the day are in the gut. Once ‘energy demand’ is satisfied, the assimilation rate will change and meals will be processed differently. Attractants coating some pellets is a good idea if you want fat fish but not a good idea if you want healthy fish. I’m getting off topic but in terms of Volume per meal, you are limited by these realties of assimilation and not about size of crumbs? I suspect that the post-masticated size is similar in both pellets.
As far as size of pellet goes, pellets should match the size of the koi- large pellets are not too large for those grinding molars ( which grind open and crush the shells of clams and cockles) and can EASILY crush a pellet in one crunch. You can often see particles of food come out of the gills as the fish chews. So too small a powder or fine a grain and you are polluting surrounding water. Juvenile fish- small pellet, pre-adult- medium pellet, adult fish, large pellet.
Basic koi nutrition requires a certain mix of ingredients/food groups and a certain amount of calories per day for growth. Once you have done that correctly, the rest is counter productive.