Pros of lagering:
- You can make lager.
Cons of lagering:
- You're not making ale.
Seriously though, the fundamental difference as I understand it is the temperature at which you are fermenting (and conditioning). In practical terms, yes, Heineken/Corona/Bud, etc. are lagers, while Guinness/Newcastle/Sierra Nevada are ales. There are a trillion subcategories and styles, but that's the bones of it.
Me? I'm an ale man. And not just because I can't ferment my beer at anything but ambient.
EDIT: Just noticed you're fermenting an Oktoberfest. Are you not lagering that?