yah none of these are really full towers

@Bananasplit_00 actually I'd make the argument they're ALL Full towers. Mid should be under 65L of volume.

Especially since we live in the age of more compact Mid towers 

full towers, as trump would say: it doesn't exist folks

@TVwazhere full tower is like what the 900D was, space for everthing and more, these are all mid towers to me. volume is also not the metric id decide between full and mid tower, because cases like the Lian Li PC-O11 would be a full tower im pretty sure and that thing is not one to me

@Bananasplit_00 That's a Super Tower

Honestly I would use volume over anything else. People often have the thought that they need a Full tower to fit hardware... Like a 360mm rad, but the Meshify C proved that wrong entirely. Or Lots of hard drives (Define R6 at 58L). E-ATX motherboards (The fake 272mm long ones anyways) can even be held in many Mid towers. Hardware should NOT be the deciding factor in what a case should be classified as. 

For reference, the PC-O11D is 54L, so on the large side for a mid tower but still definitely what I'd consider to be a mid tower. And that can theoretically hold tripple 360mm RADS, 3 HDD's and/or 6 SSD's, E-ATX boards and even two power supplies. The Evolv X at 63L can hold two system in it. 

Well being as old as I am, full towers back in the mid 90's were f'ing huge!!!  I wish I still had that one I bought back then to mod it.

And yes I agree, the naming conventions don't really make any sense any more... I just go by if the motherboard capacity is what I need, eg ATX/m-ATX and so on, and if I like the looks and features of course

I'm still in my liking dual chambers and cubist cases right now... though I am quite taken by the Thermaltake view 71 TG, just the price puts me off, but I WILL need a new case when Ryzen 2 drops as I am going back to ATX boards, and using my current cases as the server builds. Which means yet another re-config of my systems is in order, I swear |I do this at least 5-10 times per year (on various systems not the same one), LOL

Dark Base 900 is 38mm longer, 39mm thinner, and 33mm taller than the silent base 801. So you wouldn't think the volume would be that way, but alas it is. Either way the Dark Base is longer and taller, but also thinner than the 801.

Either way the total volume different is 2.25% so not crazy.

All that aside the Length and height are much more important when you are talking about adding things like a radiator. The width is only important if you are talking about adding a big air cooler. So when it comes to usable dimensions I think the 900 is overall better.

@AngryBeaver My point was mostly The 801 should definitely be a full tower.