I would suggest renting a Sprinter before buying. The downside of the Class B Sprinters is they are very small. Hard to get around each other, really you need to sit down if the other person is up. The B+ (also known as a Class C w/o the bunk over-cab) is what we ended up with, and even those are difficult to spend time in. Good for a weekend or even a week. Beyond that, you start looking for the exit.
The Airstream is very nice, I am thinking about selling my current Thor produced Airstream 40-foot motorhome and buying an Airstream trailer and towing that with the Cybertruck when it comes out. They make a 25-foot Sprinter B+, the Atlas, but it's super expensive for what you get, and you still cannot leave the driving to the Sprinter. I have the LTV version of the Atlas, the Serenity, sleeps 4 and carries 50 gallons of fresh, all while getting a reliable 18 MPG. No slides to put out if you wanna sleep at a rest stop or to worry about failing over time.
If you rent the Class B and are OK with the size (easier to park than the B+ or C's) I would prefer the Era personally, but you would have to buy it used at this point if you want the slide-out, even LTV, the originators of the Class B slide no longer make it. Perhaps the dual door Sprinter isn't made anymore.
One other thing to consider if you are considering buying a NEW Sprinter is the models that are coming out with full-time power. Giant lithium batteries that charge with solar or off a second alternator. This are amazing. You no longer have to carry LP, just charge off the sun or at a campground or even boondock and the engine can come on if the power is getting too low after a few days in the rain or parked in the shade. Lithium charges SUPER fast so you are not running the genny for hours and hours as you do with AGM so you won't run out of heat in the night. Even if you have to run the engine, it's got full emissions controls on it and you had to buy fuel for it anyway. The Winnebago Boldt (new for 2019) has a power system like that, but there are many others already.