There seem to be several camps on camper toilets: those that don't want them at all (the "don't shit where you eat" group), those that wouldn't live without them, and those that don't really think about it, don't end up with one, and wish later they'd considered it more.
I think your use case makes a big difference here. If you're primarily going to camp at established campgrounds with bathrooms, or on BLM land/national forest where you can dig a cat hole, you might not be inclined to use a camper toilet at all. If you'll be camping around cities where you have bathroom options during the day (gym, gas stations, public restrooms), but overnight it could be quite difficult to find facilities - that's when having something in the van starts making sense.
At the end of the day, this is a personal call - however, if you think you may be interested in incorporating a toilet, this is a good thing to consider as you plan your layout, to make sure you don't build yourself into a corner where you wish you had room for one but don't have a spot for it.
Let's start here because it's probably the most common approach, especially for weekend warriors and those who aren't living in their van full-time.
Real talk from experience:
The no-toilet approach works great... until it doesn't. That 2 AM urgency in pouring rain or below-freezing temperatures changes your perspective pretty quickly. Many people start with no toilet and add one later after enough miserable experiences. If you're on the fence, at least leave space in your layout where you could add one.
The middle ground between nothing and a full toilet.
These are the simplest step up - basically a bucket with a toilet seat on top.
Cost: $20-40 for commercial, or DIY for $10-15
Managing the smell:
This is the biggest concern with bucket toilets. Here's what helps:
These are the standard in RVs and are probably the most popular choice for van builds that include toilets.
Cost: $150-400 depending on model and features
Emptying routine:
The reality that people don't talk about enough: emptying a cassette is kind of gross. You pull out a 40-50 lb tank of sewage, carry it to a toilet or dump station, open the valve, and pour it out. The chemicals help, and it's sealed, but you're still dealing with a tank of waste. Some dump stations have a rinse hose, many don't. You get used to it, but it's nobody's favorite chore.
These have become increasingly popular in the van world, especially for full-time living. They separate liquid and solid waste, and use biological processes instead of chemicals.
Cost: Commercial units: $900-1200+, DIY versions: $150-400
The urine bottle situation:
This is what puts some people off, but others say it's no big deal. You're emptying a bottle of urine every 2-3 days. It's literally just urine - it doesn't smell much when fresh, and you just pour it into a toilet, down a drain, or dilute it outside (diluted urine is actually good fertilizer). Most people find this way easier than dealing with a cassette full of mixed waste.
The composting process:
When working correctly, solid waste mixed with peat moss or coconut coir (the "medium") slowly composts over weeks. The fan evaporates moisture and keeps things aerobic. By the time you empty it (1-2 months), it's mostly dried, partially composted material that doesn't smell bad and can go in the trash. This is way more appealing to most people than a tank of liquid sewage.
My take on composting toilets:
If you're living in your van full-time, this is probably the best option despite the high cost. The combination of little smell, infrequent solids emptying, and no chemicals is really appealing. Yes, $1000 is a lot for a toilet, but over a year of full-time use, the convenience is worth it to many people.
If you're camping a few weekends a month, save your money and go with a cassette or bucket system.
You probably don't need one. Use campground facilities, plan your stops, and keep a pee bottle for emergencies. Save the space and money.
A toilet starts making sense. I'd go with a cassette toilet ($200-400) as a good middle ground. Yes, emptying it is a bit gross, but it's manageable and beats the alternatives.
Get a composting toilet ($1000) if you can afford it. The reduced smell, infrequent solids emptying, and no chemicals make it worth the cost when you're using it every day.
Start with a $20 bucket toilet and see how you like having a toilet. You can always upgrade later. Don't let the lack of a fancy toilet stop you from building your van.
Leave space for a toilet but don't install one initially. Camp for a few months and see whether you actually want one.
The toilet question comes down to this: are you willing to sacrifice some space and deal with waste management in exchange for not having to leave your van in the middle of the night? There's no right answer - it depends on your priorities, use case, and squeamishness level.
Just please, whatever you do, dispose of waste properly. Nobody wants to find your poop bag on the trail or in a parking lot.