My experience for what it's worth
I had a 30L Klarstein ordered a few months ago but it took so long (because of usual brexit shenanigams)
I ended up cancelling it.
In the meantime I'd picked up an 8 gallon ( approx 38L ) pan, wort chiller, assorted bags etc.
for £60, I'm sure I've learnt a lot more about all grain brewing this way.
I can comfortably do batches up to around 18 ( probably a bit bigger, that's limit so far ) but you can also
brew double strength and liquor back.
Now I just like the simplicity of BIAB and have spent money instead moving onto a corny keg system.
The main advantage of the all in one systems that I can see is controllability of mash and boil, though
the efficiencies often don't seem much better than is possible with BIAB.
Plus there can be electrical faults with thermostats, elements, pumps etc as well as more parts to clean.
The model I looked at had a wort circulator for an even mash temp which seems advisable though plenty
of people seem to do well with straightforward boilers and hand sparging.
In a similar way as a carpenter I have lots of fancy expensive tools to make life easier but a lot of the time
I'll reach for a hand tool first if I can get the job done quicker.
That said, as Cheshire Cat said, buy cheap, buy twice, so if you go down the all in one route
get the best you can afford now and you won't regret it later.