Why does the 2 GB Clip rev.2 have >100 MB less memory available than rev.1?

I recently purchased a Sansa Clip 2GB player which I will have to return because the audio jack doesn’t hold the plug from the earphones - the cable constantly slips out.  This unit had hardware rev. 1.0, with firmware version 01.01.29F.  I formatted it before I’ll send it back.  After formatting, i.e. for an empty player, under “System Info” it said Memory 1949 MB, Free 1927 MB, the difference presumably being the space taken up by the firmware.

The replacement unit that the vendor sent me came in different packaging, had hardware rev. 2.0 and firmware v.02.01.16F.  Out of the package, this unit had a total memory of 1855 MB.   After formatting this unit, “System Info” said Memory 1855 Mb, Free 1809.  I.e. this unit, with nothing on it, had 118 MB less memory available than the first unit.

When I connected these two units to my computer (running WinXP), Windows confirmed this difference:
First unit (rev.1): Capacity 2,043,904,000 bytes = 1.90 GB
Second unit (rev.2): Capacity 1,945,862,144 bytes = 1.81 GB
Both units were set to MSC mode.

Can someone explain the difference to me and tell me whether I can do anything about it, short of sending the second unit back again and requesting a replacement in packaging identical to the first unit that hopefully will have the extra 10% of available memory?

Its 4.7% less memory, because a newer generation memory chip is used which has fewer available blocks due to more powerful error correction.

Thank you very much for the prompt answer.  I somewhat doubt the wisdom of reducing available memory (you basically get 10% less than what you expect when you buy the Sansa Clip ver.2.0, i.e. 1,800 rather than 2,000 MB).  After all, how important is it to have powerful error correction with mp3, ogg or flac audio files where one wouldn’t notice a few corrupt bytes or memory blocks.  These aren’t binary executable files where every bit has to be correct.  But I suppose the SanDisk engineers must have had good reasons for choosing this route.  Does this really extend the useful life of the unit?

Really, the v1 had some “bonus” capacity, which balances the issue out somewhat. A “2GB” flash chip usually only has ~1.86GB actual capacity (read this if you don’t understand why). So while the v2 has a little less than that, it’s only ~50MB less than promised.