It's always a balance between how much penetration you need for a given situation and how much expansion you need to impart energy. Factors such as the total amount of energy in the bullet at impact, it's sectional density, meplat, frangibility, toughness and hardness all play a part, hence why bullet construction is so important. There are times when you don't want to completely obliterate what you're shooting at and times when you want to make the biggest exit wound possible, it depends on the situation. I prefer a 150gr interlock in my .270 because it will knock down the largest game the UK has to offer whilst not obliterating a muntjac. This works for me because I want to use a single rifle/scope/bullet/load which can cover all UK game. I don't only have one rifle but my .270 is the one rifle I want to be able to do anything in the UK with and this combo is my compromise for that. I also just bought a 35 Whelen which I plan to use on large red deer in Devon this coming season which I will use with 225gr Gamekings at around 2800fps at ranges of up to 100m. I expect it to work better than the 150gr interlocks from my .270 but I wouldn't necessarily take it to the highlands and attempt to shoot reds at 250m with it as it will have a scope better suited to short range woodland stalking and the bullet drop and wind drift would be worse than the .270 at that range. Horses for courses. If I weren't shooting muntjac with the .270 and mainly shot red deer or boar I would probably use a 130gr bullet because as
@Mungo and
@Edinburgh Rifles rifles rightly say it has more energy than the 150gr.