Not sure what your goals are but if you're doing push-pull, why bother with 38mm fans? They are always noisier. I'd stay with 120x25. There will be enough pressure, your radiator is only 35mm thick.
I agree the price difference is huge and I doubt the noise/performance difference justifies it -- if you run both sets of fans at the same noise level (or roughly the same speed), you will get very similar cooling, especially as push-pull tends to diminish cooling differences.
I'm surprised how many people say they like the Gentle Giants (or is it reviewers that say this? who?). imo, they sound no better than many other fans -- and often worse when slowed to a really quiet speed. A GT 1450rpm sample at 7V develops a bnnnnnn type of tonality that's not pleasant at close quarters. 6 of these would drive me nuts.
With regard to longevity differences, you might see a difference between sleeve and ball under very hot conditions, or with the fans blowing down, but otherwise, I doubt there's any real difference.
In short, I would go the YL route.
thanks for the reply
, people who liked the gts were on another forum i asked (ocforums)
I have decided to go with YLs, but havnt been able to buy them yet due to money problems (the money i was gona use to get the fans had to be refunded due to a dispute on ebay) so i need to wait a few weeks to be able to afford them.