Does calorie content/cuo really matter?

I have a 6 month old English cocker spaniel that was on diamond naturals puppy and now is on purina one true instinct. The true instinct has shreds of chicken in it and he absolutely loves it. Could be because he’s older now that he’s not staring at me wondering where his canned food is. Anyway he loves it but the calorie/cup is way lower than other puppy foods. It’s around 370cal/cup but the diamond naturals small breed is around 450cal. So do I just feed him more? Sometimes I mix a can of wet food with it so I guess it’s a moot point but wondering if I should switch him back to the diamond naturals. The Diamond also has probiotics. The vitamin E is lower at 150 vs 400 but still seems reasonable.