Air cooled versys water cooled engines.

This is the second time I'm posting this, because my session timed out and my message was eaten up by the eater - upper of 1's and 0's in cyber space time.

Ok, to quote ICM from another thread.

exactly why i bought a DR 650.... air cooled, reliable as an anvil...loads of after market accesories available to make it a true trans africa bike....no matter where u are someone can fix it...

get the lightest bike with the best power for the trip...

look at a xt600e or dr350, xt350 as well...

the simpler the better imho

Click to expand...

Now one day I'm going to kill my KLR, either by mistake or simply by putting too many kilos on the bike. As a person who once missed a trip because of wrapping his radiator around a big rock (followed by myself embracing mother earth), I've wondered if an air cooled unit has advantages and/or disadvantages.
Do they last as long as water cooled units? How do they do heatwise in the slow technical stuff? Remember this is a 650 class engine we're talking about, not a 125.
Please fire away!