What radiator would you buy?
 

It looks like there are a few brands out there and Behr would be the OEM brand although recently they manufacture them in China. The OEM is the most expensive. Rockauto has a few brands as well. Is fitting an issue on non Behr one?
What would be a good choice?
This is for 4.4 prefacelift it that matters...

I don't know what the costs is...but the OEM was not terribly expensive when I bought mine. I only did that out of preventative maint. If the plastic neck lasted 10 years on the OEM, that was more than enough just for peace of mind.

Well, from the dealer I can get it for $520 here with discount and online is about $350 + shipping $80.
I can get Behr for $250 shipped or other brands from Rockauto for as low as $150-$190 shipped.

Went with a Behr for my 330i ... Only difference is that there isn't a drain plug on the radiator. I have heard very little about the two aside from this (and that OEM is expensive!). Technically there is another OEM provider who did make one with a drain plug, but I never could find an online provider. Finally, make sure you get the one for your (automatic) transmission. The valve/ end tank is different.

I ended up buying the Behr and it looks like for e53 it does have the drain plug.

I purchased the BEHR radiator and I didn't come across any issues. The radiator has been on there roughly about a year now and have had 0 issues. Why pay $350+???