I'm buying some additional hdd for an IBM server: in the supplier website I see, for ex:
39M4526 IBM 250GB S-ATA HOT-SWAP 3GB/S HDD
43w7598 EXPRESS 250GB SATA HOT-SWAP 3GB/S HDD
The prices are different but they seem equals. I already have some 43w7598 and they have the hotswap enclosure. Is the difference only in the package?
Updated Answer
The IBM x3550 Hard Drive Accessories Website shows that both the 43W7598 and the 39M4526 marketing part numbers have the same replacement part number of 39M4529 (see screenshot below). This appears to confirm that the drives are functionally the same and only differ from a marketing offering standpoint.
IBM x3550 250GB HDDs http://img.skitch.com/20091217-db78umky9nd6x31wracj7m1br9.jpg
Original Answer
The only difference that I could find was in the type of warranty service:
To find this information, I went to IBM's Storage Accessories & Upgrades Shop and then added one of each into the cart. At the next screen, I clicked on the product description for each to get the screens shown below. Going this route, both drives were priced at $139.00 each.
Based on the IBM Express Advantage portfolio webpage, it appears to me that the Express designation is just a marketing offering geared toward the midsized market. I wouldn't be surprised that they are offering the same products under different model numbers for different prices/markets.
IBM Express 43W7598 Drive http://img.skitch.com/20091217-gk9kfsn4nah12fefcjb6d8tf8t.jpg
IBM non-Express 39M4526 Drive http://img.skitch.com/20091217-r9mdua1ehyc5y5we4wj5wu956y.jpg