I triple-booted on an 8-years-old MacBook Pro (and OS's comparison)

So, I got my hands on an 8-years-old MacBook Pro (mid 2012), with 4GB RAM, 500GB SATA HD, and Core i5 CPU. Good thing about this, is 500GB is very large. (Compared to nowadays usual small (but faster SSD) 128GB - too small to dual boot.) My MacBook P...