So there are 2 ways to download ISOs for Windows 10:
Windows 10 <--- Downloads a tool you can use to generate your own ISO.
Windows 10 ISO <--- Downloads the ISO straight from MS (same as MSDN)
If you try and access the second page from a Windows PC (with IE, FF and Chrome), you'll get redirected to the first. Use a browser-agent spoofer (e.g. chrome extension) to change it to safari to avoid getting redirected.
Anyway, using the MCT (media-creation-tool), you have the option of making an ISO that contains EITHER Home or Pro with BOTH x32 AND x64.
Downloading from MS you can download one 32-bit ISO that contains BOTH Home and Pro, and one 64-bit ISO that also contains BOTH Home and Pro.
So if you have both ISOs from either source, you have every possible installation source (not sure how to word it), e.g.
Except there's a big difference in the file sizes.
If you download the ISOs from MS-page, they're both ~3GB, =6GB total
If you generate both ISOs from the tool, they're both ~6GB, =12GB total.
Long post, but can someone explain the difference between the file sizes?