@datalevels @angristan (Sorry, deleted original toot lol)
Easy, you add another entry. If your (U)EFI supports it, you can go to the boot device menu and choose which system to boot. If you don't, you can still change the boot order from within an OS with `efibootmgr` or equivalent.
There's also alternatives which are kind of a mix of the best of both worlds, see rEFInd http://www.rodsbooks.com/refind/