For dragon I wouldn't recommend any headset with the small strip mics. They're good for skype but you'll get a higher typo ratio / slower WPM on dragon. And no, I haven't tried everyone on the market but they're all omni directional & have no diaphragm, you don't wanna transcribe with that.
The snowball is a good mic. Cartoid directional (front) it has a large diaphragm which can be a good or bad thing depending on your voice.
Let me give you the real truth about mics since I've had a studio for 15 years now. I've learned a lot about mics over the years.
You want a VOCAL mic for The Dragon. Ideally a cartoid (most mics are cartoid) with a medium diaphragm. The yeti-blackout is slightly higher end ($129 gamestop). It's great mic that can switch between cartoid to bi-directional to omni-directional. Radio shack also sells a cheaper version ($39.99) that sounds incredible and has great frequency response:
https://www.radioshack.com/products...CPXg3Oiwyc4CFYtahgodlDYElg&variant=5717705861
HOWEVER, anytime I buy a mic for a specific purpose (voice, toms, snares, etc), let me tell you what I do it's what any engineer would recommend.
Your voice, vocal chords and lungs all compose a unique instrument. As basic as this fact is it's extremely important to understand. When I meet with singers off CL I test all 4 of my primary studio mics. Manley Reference Cartoid, Royer, Behringer, Audio Technica. They always get excited when they see the Manely. It's an expensive ass mic I got at an auction years back.
But here's the thing... 10/10 times I'll crawl into my attic and take out a box of older mics. Then I'll A/B test their voice through every single mic I have. And when you see a cheaper Behringer beating out a Manley Reference.... which is suppose to be one of the best mics in the world.... you'll understand how important voice matching is.
So GO OUT and buy 3 mics from 3 different local stores. Figure out what you're willing to spend then spend 3 times that amount and keep all 3 receipts.
Take each mic home. Test it with the dragon and your voice. Then test your WPM & typos. Which mic gives you the faster WPM with the least typos? That's all that matters.
For me it's not yeti, manely, behringer, etc.... it's that cheap ass cartoid I bought from radio shack like 8 years ago. When I bought that thing I thought "what a piece of shit". But I had bought other shit from radioshack that impressed me. And when I brought it home and tried it I was like "damn! this sounds really good!" And years later I installed dragon and compared it to other mics. That specific mic gives me the fastest WPM with barely any typos. If you A/B test like this and also train Dragon you can easily get 250+ WPM transcribing done with very little typos.
So to sum up, there is no "best" mic. There's simply which mics performs the best for the specific person or purpose you need.