||01-19-2013 04:27 PM
Guardian Angel is really handy for the passive, which generally causes significant problems for Bruisers and Assassins diving on you - or causes your dives to have some room for error if you're an Assassin or Bruiser. For a carry I'd say Guardian Angel is going to be better in pretty much every circumstance, as it significantly extends the time an enemy needs to be on top of you to take you out for good - what with the delay in resurrection were the rest of your team can go to work, then you can pop up and clean up. Warmog's offers a lot of health, but against a determined assassin or bruiser will only extend your lifespan by ~1-2 seconds without other defensive items or steroids. That said, Guardian Angel is only useful if your team is sticking together - if you die alone the passive isn't going to help out worth didly. Guardian Angel is also a handy way to counter champions with skills that re-set on kills and assissts, such as Darius and Katarina.
Warmog's is going to be better if you're dueling or trying to split-push, as if you're caught out the revival passive on Guardian Angel is only going to be wasted. If you have a decent chunk of resistances, attack speed slows, spell-shields, abilities that boost your EHP by a percentage, or abilities that cost health Warmog's is also probably going to be a better choice - as you're going to last as long or longer then the revival delay Guardian Angel grants. Health is incredibly cost-effective early game, so if you get Warmog's you may want to consider picking it up as the first major item - were you'll more than double your EHP with it. If you can't put life steal or spell vampirisim to much use Warmog's is also going to be a really useful pick-up for the sustain it offers.
More or less I'd say if you're a front-liner Warmog's is probably going to be better, if you're a back-liner Guardian Angel is probably going to be better.