I read this MB forum often because the MB owners tend to have a lot of experience with maintenance and driving bigger campers, good, practical DIY experience, etc., a good deal of which translates to anyone driving with a camper bolted to a full size truck. I've been going the F550 route for the past 15+ years in an Earthroamer. The advice I see above is sound. I have been looking to go a little larger in order to spend more time traveling & living aboard vs what we've been doing which is mostly shorter trips <month. I am currently leaning towards Bliss, just looking for a good truck to put it on with seating for five and a pass through. The older MB's I've seen are impressive and built to a different requirement than the US trucks which for a variety of reasons seem every year to gain hp & ft lbs but harder to keep running and with a shortened lifespan....maybe soon they will all be biodegradable. As near as I can tell MB designed the trucks we can legally import (25+ years old?) to perform on&offroad, to last a long time and to carry heavy loads easily, simply and relying on proven technology & engineering in extreme terrain & conditions. If there was a reliable US-based source of MB truck parts and some decent MB shops with trained mechs for some of the big/complex jobs, I'd already have gotten an MB. Haven't yet found that to be the case and still thinking over whether to dive in to the commitment. I try to do most of my own wrenching but not looking for a part-time job as an apprentice MB mechanic with nothing much more than the internet for a teacher. My 2cents:
1. I would really focus on what you're looking to do travel-wise, the length of your trips, where you are going and how much space you will realistically need. IME, the Earthroamer is great for short to multi-week family trips but lacks the "living room/office" space needed for long term travel if you are accustomed to living in a real house. It is warm (or cool), comfortable and dry in all weather, a great base for all sorts of backcountry adventure, can negotiate any paved or decent dirt road you'll find and will be more mobility-limited by vehicle height than any other factor. Practically speaking, it is also a great hotel on wheels.
2. Think hard and honestly about whether or not you are going to spend the vast majority of your time on road or in easy to access campgrounds/sites in the USA/Canada. It is easy to have a dream about being in a relaxed zen-state churning up a mountainside talus field on your portal axles and huge tires, getting to a remote campsite by a mountain lake, then firing up the espresso machine or cracking open some cool daddies and admiring the commanding views of the Cordillera Huayhuash as you and the Mrs. pore over a mapset to find more unobtanium camping on your way south to the Carreterra Austral and more adventure...the reality is often Walmart parking lot listening to the teens doing donuts, smashing bottles and random acts of inhumanity in the parking lot at 2AM as you contemplate poorly-aimed gang-banger 9mm zipping through fiberglass camper walls or racked and stacked at a $150 a night RV "campsite" with 4' separation between rigs, everyone has a campfire going in the middle of summer and some kind of domestic drama/howling dog/drum circle/music on too loud/etc. as you drive through urban terrain en route to more mundane outings like getting to an early out of town dentist's appointments for your kids, etc. where camping was a great alternative to hotels.
2. True offroad will require a vehicle specifically designed for it (certain MB, Iveco, MAN, LMTV-type rigs all come to mind) having a high endurance/durability offroad setup designed for the full-time WEIGHT of a camper...things like the right gearing, locking diffs, CTIS, appropriate axles/GAWR, etc. IMO.....and of course wherever there is a will there is always a way....but IMO, newer (than 7.3 and 5.9 generations), camper-loaded F550/5500-type chassis trucks are great but not really designed to be field-repairable and not really [no matter what wheels/tires and shocks non-OEM hodgepodge you equip them with] well-designed for much rough offroading, deep mud&sand or solo travels deep into the North American bush, even less for 3rd world bush for a multitude of reasons, unless you have a wealthy Frenchman's approach to your time and money. That said, these US chassis trucks when not overloaded from the factory are great for the North American highways, decent on dirt roads and can clamber into a nice backcountry campsite with proper planning and a little patience. One of their real strengths is that they are great for getting around in winter with the right tires (and some chains at the ready). I'm conservative with trip and route plans, have spent more than enough time overseas not in a camper and roam the US and Canada exclusively, and have never had a real issue getting into some great spots in an F550.
3. I would visit some of the companies who make the rigs you think fit your budget and goals and spend time in them, maybe try to rent one or something similar and see what you like and don't like. Really look through all the systems and see if they pass the sniff test. There always seem to be great campers for sale on this site and others that clearly were purchased, used on a few trips and then the owners realized it was the wrong rig, wrong lifestyle, etc. and now selling. Save yourself this and take as close a look as you can at what's out there.
4. Other things that are easy to overlook are things like camper size, parking, etc. unless you plan to live on the road. Do you have a big flat driveway space, maybe even a garage with 14' RV door to keep your rig out of the weather? If it's going to live outside, do you have safe parking? A lot of neighborhoods, towns and counties have rules about parking campers that can be problematic-impossible to work around. If you are mostly going to be in North America and do end up going the 6.0, 6.4, 6.6, 6.7 newer US diesel route with an F550/5500, I would try to find a gently used rig that fits your spec, take a close look at how much it weighs...ideally you are a good deal under front and especially rear GAWR loaded for a trip because for some reason US chassis truck engineers determined that having ~2x the load on the rear axle vs the front is what they figure a loaded 550/5500 should be. I do not think they had much offroad in mind with this design and without chains or at least dedicated siped tires, going downhill on ice can be exciting as the rear end really wants to swap places with the front....but no problem with patience/chains/etc. If you want a simple and effective suspension, make the day trip to Pohl Springworks in Spokane Valley WA...they will make short work of dialing in some custom shocks, coils and leaf springs that should last as long as the truck (I am going on 6 years trouble-free driving with zero maintenance other than keeping stuff clean and rust-free). There are a LOT of folks having good luck with kelderman on F550's and the new Liquid Spring seems pretty amazing as well. For me the real question is how much more capability do you get for the money and reliability, neither kelderman nor liquid spring was an option on my truck. You can look at my profile pic and past comments (search "315/80r22") rel to tires. If you are worried about the motor, check out DFC up in Edmonton or one of the many other reputable engine reman companies. Drop in a new motor spec'd to what you want and you'll be good for a long, long time, especially in Canada.
If I make the decision to start spending a lot more time on the road in the future, I would probably try to go the Bliss route (or maybe pre-owned Unicat) with an importable MB crew cab/doka, chiefly because I would want more room and travel in the winter so I need 4x4 plus I'd want a pre-Def, etc. motor....at which point I would just have to dive in on the parts and maintenance challenge as well. We'll see.
