@ssp3 Agreed on battery life, although I'd be surprised if a 128 GB SSD drew more power than a 128 GB HDD.
I notice the power issue when I plug-in to my DLSD my external FW 800 enclosure containing the 4 TB Samsung 860 PRO SATA III SSD, and, simultaneously, my external FW 400 enclosure containing the 2 TB Samsung 860 PRO SATA III SSD. The DLSD's screen, once booted into Mac OS X, simply goes black not too long after plugging both in simultaneously. That 4 TB drive is not even TLC, but MLC, which I'm sure adds to the power draw.
In practice, though, I know 1 TB MLC SSDs + Marvel adapter are 100% fine on the mini, even 1.5GHz model, so no problems at all in there. The DLSD's 2 TB M.2 is also just fine, but I never had a working battery with it (and was never able to source a replacement), but otherwise the additional power draw could make me reconsider just to prolong battery duration.
I don't find more than 128 GB overkill, though, my Diablo II installations alone are 100 GB (because I installed every possible version, and actually use my characters across multiple versions for various cross-version perks), but depending on how people use Mac OS, 128 GB can be enough, but not as a proper daily driver you put all your files on, IMO.
A properly-formatted / partitioned 2 TB drive will always boot no different from a 128 GB one, too. An improperly-formatted 128 GB drive will also not always boot. So I don't see any point there.