[vhodges]

The size difference can be substantial.

I have an Antec something-500 from 15 years ago and a Caselabs ITX case that is larger (for custom cooling, etc - I never did use the space) and in 2018 transplanted the guts into a SFF from Sliger and I could fit four of my new case into the Caselabs case - and they are commanding quite the premium in the afterlife.

Height and Width are less than my MacBook Pro (deeper of course but still only 13.5cm)

I don't compromise on much, sure there's only a single PCIe slot but it's got a full size GPU in it (rx5700 reference design), a 650W Gold modular (SFX) power supply. RAM is 16G (lots for my use case - the MB is 2015, not sure it supports more - but with 64G sticks I don't think two slots is much of a limit), a M2 PCIe drive and a separate 2.5" SSD, two Noctua 120mm case fans and a decent after market CPU cooler. It's quiet and it runs cool.

Lastly on price. A good quality power supply is going to run you 150-200 and most decent cases are in the 150-200 range without a power supply anyways. These are small run manufacturers too so that makes them pricy too, but they'll last 5-10 years (eg a couple of MB upgrades) so worth the investment to some.

They are a pain in the ass to build in though :). (The Ghost looks a bit easier but wasn't really available at the time)

[SergeAx]

One PCI slot is effectively zero PCI slots because I don't know who is seriously using internal graphics. Maybe as a temporary solution to get things up and running and buy GPU later (doesn't work with AMD, though). This, by the way, is another perk of a desktop PC - the ability to postpone some upgrades.

To expand the RAM you will have to buy new sticks first and then try to sell old ones, with the discount, of course. My ATX board supports 4 sticks, so I could start with just one 16Gb (with bandwidth penalty, but still) and pump it up to 64Gb without any reselling hussle. I am also a happy owner of ASRock B350 motherboard so it is 6 years from Zen 1 to Zen 3 all the way for me.

I don't even want to start bragging about switching from air to water cooling for silence sake, I don't think it is even possible with mini ITX form factor.

So, once again, for me the main perk of desktop PC is upgradability, and mini ITX seriously impairs that.

[vhodges]

I don't game (but would like to be able too). I ran intel integrated graphics for 5 years and never missed a thing ;).

I put 16G in my machine in '15 and rarely exceed 3-4G daily use even today (and for a long time 1-2G daily - I recently switched to Budgie desktop so it's jumped a bit). At this point I'd just buy new ram and the two sticks I have go into the surplus pile but my motherboard (depend on source) only supports 16 (it's oldish also from 2015)

There are water cooling for SFF cases (mine can take a 120MM radiator for instance - the ghost mentioned upthread can take up to a full 360 with the tophat) but I put a Noctua CPU cooler in and changed out the fan on it. Stays nice and cool. My Caselabs itx case could do up to 3 360MM Radiators but was not SFF (by a large amount!).

On the upgrade path, it's so long between that I usually just build a new machine, 6+ years so far on my current desktop and good enough until I find it not. By then, DDR5. PCIE 4.x, etc, etc

I am not trying to convince you to get one, just show that there's a market for SFF... just like there's one for latops, rackmounts, NUCS, stickpcs, Pis and yes even EATX Threadripper monsters in cases on casters ;)

[SergeAx]

With your circumstances (internal graphics, 4GB RAM tops) I would consider using Raspberry PI 4 as a desktop computer (seriously, no sarcasm). If you are interested in reduced footprint, take a look at Lenovo ThinkCentre Tiny series: they have a VESA mount to hang behind the monitor and the price starts around $400 (your ITX case + PSU)

[vhodges]

No quite enough CPU ;). It's getting a bit dated of course, but my machine is running a Devils Canyon 4790k (at stock speeds), 16G ram, 1.5TB of storage (NVME M2 and a 2.5" drive) and a rx5700.

[ctippett]

If you don’t mind limiting your CPU choices, there’s nothing stopping you from using one of AMD’s CPUs that come with integrated graphics. I did this for a short while with a Ryzen 5 2400G before purchasing an external graphics card (and eventually replacing the CPU too).