1. The new Instax Neo. Pros: finally a serious camera from Fujifilm. Cons: Small images. No monochrome.
2. Instax 210. Pros: Nice sized photographs. Great color. Cons: A joke of a camera, no monochrome.
3. A Polaroid Land camera: Pros: both color and monochrome. Good image size. Cons: Old camera, hard to find in China, questionable reliability.
Tough call.....each option has an appeal to me.
You could also shoot instant in a "serious" camera. Peel-apart Fuji in my Speed Graphic is a lot of fun, and a lot easier than stuffing Instax into 4x5 holders individually.
To me, neither the equipment nor the film define "serious" photography; rather it is the intent of the photographer and the images produced.
In 2006 I was in Yosemite and had my SX-70 with me. I made a photo of El Capitan and of Half Dome that impressed me with the creaminess and tone of the colors - right then I knew I had two keepers (which I later scanned and enlarged to 8x10). These two are among my very favorite photos that I've made over the last 30 years with various formats and media. I suppose if I'd used 35mm, or whatever - even digital, I might be able to tweak the results to look similar -- but I knew the shots had an amazing look right after I took them.
Marie Consindas and Andy Warhol has been doing serious work. When I shot professionally back in the day, I only use Polaroid to proof for the "real" film. I'm not Consindas nor Warhol, but Polaroids by them are precious art objects.
I like the Polaroid 100, metal body and tripod ready. Do a battery conversion and the only problem is you will occasionally find one with a bad electronic board easy to make a pin hole camera out of those. clean the rollers, and start shooting. The 110 a and B's are the Cadillac's. The only tools I use are a hacksaw and file, mine may not be as pretty as the pro's conversations but they work great. Only problem is finding the camera for a decent price with a good lens, then get a back, I have even used backs from the 100's, a lot more work testing and fitting. Plus lots of information to be found on line.
People sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf.