I installed Ubuntu 16.04 LTS as my second OS.
When I choose Ubuntu at the boot menu, it takes around 2.5 minutes, whereas Windows 10 boots in around 30 seconds.
Also, when I choose to boot into Ubuntu, GRUB seems like it's glitching up or something because it hangs for 20 seconds or so.
See systemd-analyze screenshots below:
Here is startup.svg:
http://svgur.com/i/39v.svg