ShadowMaker Pro costs $36 for one year, while AOMEI Backupper costs $39.95. ShadowMaker Pro takes up about 1/2 the disk space as Backupper, and their bootable USB stick should work with current systems with Secure Boot active, while AOMEI's requires a quick/easy modification. Both do the same thing -- clone a hard disk partition(s) to a VHD. That said, partly due to their long history with GOTD, partly because they've been doing backup software for such a long time, I personally would lean towards Backupper, though when it comes to actually paying for backup software my money goes to O&O.
The GOTD download is a downloader, which downloads sm_free_x64.exe [152,270KB]. The app installs in Program Files (x86), adds an empty c:\Boot\ folder, plus 3 folders holding 389 files in 105 folders taking up 28MB in Users\ [UserName]\ AppData\ Local\. The registry get an uninstall key plus one for the app, and entries for the 2 new services ShadowMaker Pro installs.