Following discussion with Johan (@jarwidmark) on the topic of express files, here are the screenshots to give an idea of the difference in Donwload size and Storage Size between Express Files and Standard Compressed KBs…
Microsoft says it’s 2 to 3 times bigger to get Express Files…Screenshot below seem to show more like a 10 Fold Download Size difference.
Setup was done on 2 clean WSUS servers, running on top of Fully Patched 2012 R2 servers, same config exactly. Same setup, same approvals, same products, just the check box ON or OFF for Express Files..
On server 1:
On Server 2:
and here it goes…
Automatic approval rule (same on both servers.
executed on WSUS 1
executed on WSUS 2…exactly the same number of updates….but:
On server 1:
On server 2:
you spotted it? no? let me zoom for you 
On server 2:
On Server 1:
THATS IS 5,7 TIMES BIGGER WITH EXPRESS FILES.
But if you plan your storage accordingly, it is worth the ride when it gets to the distribution and installation on client step…but for now, i’l just let those two download everything.
Distribution metrics will be for another post, so will storage on WSUS, because for now, all we can say is it’s downloading nearly 6 time more data…
Enjoy,
PierrE.
redkaffe 
Thanks a lot.
A question please. When i use SCCM and Windows 10 Servicing for upgrade W10, used express files is there better?
Hi David,
As far as I know, SCCM doesn’t use Express Installation Files in it’s implementation of WSUS.
It’s only usefull for stand alone WSUS servers…not SCCM piloted ones.
best regards,
Pierre.
Ok, now it’s available SCCM CB1702 implements it, see my new blog post about it…
Ping : ENGLISH – SCCM 1702 Express Files for WSUS… beware of disk space… | redkaffe