I suspect there's probably still a lot of overlap between Tested.com and GB from back in the Whiskey media days, but for those who aren't regulars, they did a quick break-down of the default drive vs. full SSD vs. Hybrid drives.
TL;DR of the video is that SSDs are up to 20 seconds quicker in some places than the default, but that's only if you're willing to spend almost as much on the drive as you did on the console.
Personally I think the way to go is still to just get as big a standard drive as possible; I'm not getting paid to play, so there's no "Time is money, yo" aspect to it. Of course this is all unless/until there's another Skyrim situation where it.takes.a.long.time.to.load.for.each.door.I.open.