iPhone 3g User Memory size (RAM)

[Robcoffee]

I have been using sysinfoplus to study physical memory compared to user memory over 3 x 3g 16gb iphones and I have noticed something strange. Obviously all 3 have the 116mbytes of Physical Memory, but the user memory size is different on each:-

3g 16gb 3.0 stock firmware, Redsnow jailbreak, o2 sim activated -
86mbytes of user memory.

3g 16gb 3.0 custom firmware (1,522mbytes system partition), ultrasn0wed,
88mbytes of user memory.

3g 16gb 3.0.1 stock firmware, Redsnow jailbreak, ultrasn0wed,
90mbytes of user memory.

In an ideal situation the more user memory the better, but I have no idea why these 3 have 3 different settings. I could put the custom firmware down as the reason for a difference, except the two stock firmwares are different - unless increased user memory is a hidden feature of 3.0.1?

EDIT:- Just upgraded the 3.0 custom firmware iPhone to 3.0.1 by DFU restore, redsnowed, ultrasn0w, sbsettings and sysinfo plus. User Memory is now 90 mbytes on this one as well - so it looks like 3.0.1 has managed to give a little bit more user ram.