Less termination of life based on numbers or some version of (sentience * number of individuals)? I find it hard to believe the sheer number of individual insects killed during harvest could match the killing of one cow, calorie for calorie.

Also, what if we increase the calories of the animal we choose to slaughter, say we start raising massive whale-sized animals instead, would that tip the scales?

Insects do not have the same level of sentience as birds and mammals.

However, do keep in mind that a large proportion of agricultural output is used to feed animals.

It takes 20 to 40 plant calories to raise one calorie of beef. So slaughtering a cow kills 20 to 40 times the number of lives as eating plants directly.