I'm going to probably differ from a lot of people here.
My current grinder started life as an eerf cut by a local waterjet shop, but I've modified it beyond recognition to my own liking.
That said I've ran a number of factory made grinders at other shops, and in all honesty if I could pick a new free grinder out tomorrow, it would be a variable speed square wheel or Bee.
The Bee/Wilton grinders are surprisingly smooth and pleasant to run. and as is so often overlooked, designed from the beginning for dust collection. That's the big thing right there. No matter what you cobble together, it will never be as good as something designed from the beginning with dust shrouding.
As for a more popular option, I'd really have to go with either Bader or burrking. They both have dust shrouding available as a factory option (as goofy looking as the Bader setup is) and even more importantly, they are both companies that are well proven.
When forged in fire eventually dies, and the massive influx of people starting out in knifemaking becomes a thing of the past, I'd be willing to bet a lot of these new grinder companies will start having hard times.
Bader and Burrking have both been around forever, and both sell so much to industry that they could easily exist without knifemakers.
If I'm buying a new machine, I want it to be from a company I know I'll be able to phone up and order parts from in 20-30 years.