Older 4.4i engines vs. newer ones?

[faz]

When a local dealership shop foreman was test driving my wife's 328i for a power steering issue with me yesterday, we were talking about my X5 and my looking at possibly upgrading to a 4.4i sometime in future. He mentioned that the older 4.4i engines (2003 for example) were almost bullet proof and would run forever if maintained properly (cooling, oil, etc.)

Not that I am interested in upgrading anytime soon, but for the sake of discussion alone, I would like to hear from those who are more familiar with these engines and differences between them (not just the hp number differences.)

Is this true? What model years of 4.4i would be a better *overall* option for someone looking into them from an engine/transmission point of view?