new car, '05 4.4 or 03-04 4.6? Help...

[user1000]

Hello to everyone, this is my first thread but i have been lurking in the shadows for a bit now reading up old threads and gathering intel

i need some help choosing my new truck. I am looking at either a 2005 4.4(i was told that year is the better out of all) or a 2003-2004 4.6is. Both would have a less then 150 000km. Obviously performance is better on the 4.6is, my main concern is not to spend too much time at the dealers.

Now i am not a newb to cars and understand that i am buying a 6 year old BMW that comes with its own headaches. However is there specific engine and other hard to diagnose/long time time to fix/expensive problem spots to watch out for?
i was told that the 4.4 have bulletproof engines until they overheat due to not changing the radiator. After it over heats once it will always have problems with that.
the 4.6is are generally better built/reliable then the 4.4's? are the same parts more expensive just because it is a higher performance just like the M series is more expensive then the regular models?

I appreciate any help guys and sadly have a feeling that i will be much more active on here once i do have my SUV but i guess problems come with the territory. I just want to enjoy the ride thats why i am going for a beemer
Cheers