Difference in Space used with Win 7 update in two computers

[barsim]

One of the machines with Win 7 Pro the other with Win 7 Home premium, after updating both machines with same amount of files (regarding the space they represent, in this case: 268 MB) the Pro signaling substantially more space used than the other one with Home, which is not significant (no change signaled in HD properties).
What is the explanation for this?
Thank you

 

[NoelDP]

There are any number of reasons why two similar computers may have differing update 'sizes' - they include.
1) different hardware versions - leading to different required updates
2) different update paths - leading to differing required histories for updates.

Generally, if two machines with identical hardware and preinstalled software are run from the same date to current, within 24 hours of first boot they will have noticeably different registries, and within a month could well have markedly different update requirements.
Often, Pro and Home Premium machines even from the same manufacturer will have different software pre-installed.

Unless you discover that updates are failing for some reason, then there is no reason to worry.