X-heads vs J-heads: what's the difference??

Not that stock heads suck but cost wise it's hard to argue spending money on them isn't the most cost effective solution. And I don't buy some don't care about performance at all, or otherwise most modern family cars wouldn't make the power they do, embarrassing most older performance cars. Even a slant six has over twice the power needed to be able to drive around, technically making it a performance engine.