Dylan, my two-penneth:
Firstly, Bimobil is an excellent company building good quality trucks. They don't do bling or gizmos, but if you search "German Television" on YouTube, Sven Herzog has many videos on (static, at shows) Bimobils, which feature interviews the company CEO, who seems refreshingly honest, not full of BS. You can use the subtitle/translate function.
Everyone I have met with a Bimobil, on whatever chassis, has said great things about their bodies. Bimobil's most innovative feature is a spice rack (and the big window thing), but in real life most of the "features" people coo and ooooh about on their ultimate builds are unnecessary crap. For instance, a bank of LED spotlights, turning night into day, can be: a) unusable on the road, b) unnecessary if you simply drive in daylight rather than at night. Why on earth would you choose to drive, especially offroad, at night?
Similarly, "offroad capability" is just a nonsense in many cases. I have a Unimog 435, and a lot of people say "ohhh, can go anywhere, blah"... but, no, it can't, mainly because the limit is *ME* sitting in the driver's seat. In practice, if you live in one of these trucks you drive slowly, you take care and don't drive to extremes. It's my home. I use the 4x4, but I've never used the full axle diff locks setting. My brain stops me before then.
I used to fly small aircraft, and the feeling I get of being the weakest link in the chain is very similar... it is my own skill and experience that is the problem, not the truck (or the plane). So I often let discretion be the better part of valour and I turn the truck around or stop. For instance, I am sitting in the Unimog on the edge of a lovely beach in southern Italy (as I type this), but note I am on the *edge* of the beach, not actually *on* the beach. It makes no difference if I am in a Unimog, an Atego or a Sprinter or a 4x4 Fiat Panda... whatever... this is where my brain says "don't be daft, stop here you idiot, unless you enjoy digging".
The Merc Atego is an excellent truck with simple design and very strong reliability, (they survive ultimate abuse by local council and utility drivers over millions of miles) and I often find myself longing for a "normal" mid-truck chassis like this. Everything in life is a compromise, and the Atego seems to do that compromise very well. Size of a truck is often the limiting factor, not ultimate extreme off-road capability, and the Unimog is similar size to an Atego but is compromised by weight loading limits, while the Atego usually gives you far more flexibility in load carrying capability, plus simplicity. Going for a larger truck than an Atego (eg an Arocs) will bring its own new limitations, and while 300+ bhp and a more glamorous cab and chassis with giant tyres and a big wide and tall cabin sounds great, there are as many disadvantages as advantages in doing that (not least is the expense).
The Atego is a compact, simple and stable platform and I have never heard any complaints about the chassis. Support from Mercedes is available in virtually every town/city, and every independent truck garage is familiar with the Atego, and servicing and repair and parts availability (genuine and non-genuine Mercedes) is easy and often cheap.
Of course Ategos are slow in absolute terms, but I always see Ategos keeping up with every other vehicle, and in most of Europe you have an 80kph (50mph) limit on normal roads, anyhow. Municipal Ategos get absolutely hammered day in, day out, and they survive perfectly well. I often drive my Unimog at 70-75kph where the roads are free and open, and am constantly overtaken by refuse-body Ategos (with smaller 140 bhp 4-cyl engines), who seem to fly past, uphill and down dale.
One advantage of driving slowly is that you can safely lower your tyre pressures on the road, without danger, so that solves any harsh ride issues, easily and cheaply. I can use 3 bar on the Unimog with no danger of tyre overheating on tarmac, if I stick to sub-80kph. Comfy, grippy, easy and pleasant and I can get effective grip/comfort off road at those same pressures, saving all the faff of airing up/down constantly.
Just choose your own compromise.
I wouldn't hesitate to buy an Atego. In fact, I would buy the smallest and simplest and lowest power manual 4x4 version I could find (rather than the biggest and best version). For instance, 335/80R20 or 12.5 inch tyres are entirely adequate for this truck. Bigger, heavier tyres? No thanks.
Just my opinions. Good luck!