Personally I prefer 3.5 inch mechanical hard drives. The 3,1 is a computer that starts, reboots or shuts down slower than others anyway. After the novelty of a slightly faster boot with an ssd has faded you are left with having a makeshift physical support for an ssd in bay #1, above the fan cage, unless you want to wait a few weeks for a thingie to adapt it to a drawer. With modern 7200 rpm and large buffer WD & Seagate hard disks, you get ample space, reliability and once the operating system has started, not much of a difference in system response. Just my thoughts. The choice is yours, of course.