Sleeve bearing fans are generally cheaper, but have little or no difference in noise. 99% of high performance fan noise is generated by the fan blade rotation and air rush it produces. The better fans use ball bearings and have longer life. I have had sleeve bearing type fans sieze and / or fail, but never had that trouble with ball bearing fans. In theory, a ball bearing fan is slightly noisier, but it tends to quiet a bit as it breaks in. On the other hand, a sleeve bearing can be quiet, but won't give you much warning should it start to stick or fail.
Bottom line ... go with a ball bearing fan! Good luck.