How do modern submarines differ from past submarines?

1. Can stay under water forever. Non-nuke subs had to surface to re-charge their systems. 2. Cleaner air to breath, better food to eat, more space to move around in. 3. Can go deeper than a non-nuke sub. 4. Can go faster than a non-nuke sub. 5. Are quieter than a non-nuke sub. 6. Carry deadlier weapons than a non-nuke sub.