A Buyer’s Conundrum: Call of Duty: World at War -vs- Left 4 Dead

You’ve got £30-40 set aside to get your shooter fix; which one of these recent releases should you shell out for? This is the conundrum we face.
Join me, if you will, in drawing a mental Venn diagram comparing overlapping aspects of both games, and the aspects which make each game stand out.
Comparisons
- Production value; both games run on rock-solid engines and have been honed doubtless many times over.
- Intense, sweaty, edge-of-seat action. In a good way. Honest.
- Longevity; CoD: WaW’s levelling and perk/weapon unlock system will be similar to that of CoD 4, so will keep players returning again and again. L4D’s “AI Director” does an admirable job of ensuring that, even though you’re essentially replaying the same levels over and over, no experience is ever exactly the same. Plus, it’s Valve. They fooking love providing extra content as the months go by.
- Bloody good… ness; both titles are in the upper echelon of shooter releases this year, hence why we’re trying to decide which one to buy.