Iron Golem, Stone Golem, Shield or rune gardian

[durza120]

I was wondering what would be a better choice...To make an Iron golem, greater stone golem, a shield Guardian, or a rune Guardian.

And not just which one is more powerful, but what would be the smartest choice, taking into account the ac, xp requirement, spell lvl requirement, and abilities.

 

[Goolpsy]

Except for Rune guardian costing twice as much as a shield guardian.. it is really a more potent protector...