Neither....I guess I'll call this #3...On center lung, broadside shots I want a bullet that will have an exit wound...On high shoulder shots (bullet through the shoulder blades) or on quartering shots I would rather see a bullet that is found under the hide on the off side...(I am assuming we are talking about centerfire rifles and the quarry is deer)...I have used bullets that "always" left an exit wound and I've used bullets that "never" had exit wounds....the "softer" bullets will drop a deer quicker with a center lung shot...I'm talking within 20-50 yards and I've used bullets that always went through...leaving an exit wound about the size of a quarter...on center lung shots these deer required more tracking and would go 75-125 yards...
On high shoulder shots...they drop....With this type bullet, you have enough penetration that you can take a high shouder shot and drop them (this is very important in Eastern NC because of the swamps...I'm a pretty good tracker...but its hard to find a blood trail in 4-8 inches of water)...Also with this type bullet, if you are sitting over a field and don't mind if the deer runs aways you can take a center lung shot...if you have let the deer get 50 yards or so out in the field...they never make it back to the woods...

Playing "devils advocate"...a lung shot deer will leave a blood trail...they bleed through the mouth and nose....over 35 years ago I used a 22-250 to control the deer herd on our farms...This was before Partitions/Bear Claws etc...using plain old Remington 55gr hp, I killed many, many deer....with center lung shots, I had a blood trail....Its just not as "heavy" as pass throughs...

By picking a bullet that leaves an exit wound on broadside center lung shots and that stays in the animalon quartering and shoulder shots you have insured yourself that you have maximum energy transfer and more than enough penetration to get into the vitals and quickly do its job...