I have to disagree, You apply heat to the known hotpoints. Where as with the oven fix you're heating the hotpoints, which is fair enough but at the same time you're also heating parts of the board that arent problematic.
To use an analogy.
Oven baking is akin to nukes and killing\wounding innocents, Where as the heatgun is akin to a surgical strike team.
Both work, I'd just prefer the precise approach. And as said, I've fixed plenty, with only as single Xbox 360 RRODing again, and 3 PS3s, none have YLOD'd again. Where as I know people who have had to oven bake their systems more than once.
You can not accurately control the temperatures put out by the heatgun, and with the oven method, if its properly wrapped and protected, very little heat gets to the rest of the board.
I am approaching my 80th RROD fix, and I started with heatguns. Even with a £150 one I was getting issues keeping constant even heating and keeping set temperatures. And the few that I did had issues, once I started doing oven bakes the failure rate plummeted.
For a beginner, the oven system is the easiest and safest option, as well as the cheapest.