I have a couple of pre-Flow kendama and one of their Flow sized kendama and I definitely like the size of the Flow. The build on the ones that I've see is good and they are the only ones I've seen that have the cups a different wood. I've not tried their latest however so I can't speak about those.
I'm not very familiar with the history of Sol Kendamas except that it was started by Chad Covington and his brother Shelton. They pretty much have 3 different kinds of kendamas available; the Sol Flow, Sol Vibe, and Sol Pioneer. The Sol Flows are a bit bigger than standard sized kendamas (bigger than Krom Slaydawgs, smaller than Terra LBBs). They're all natty setups (no paint or any kind of finishes) and come in a variety of wood choices/combinations. The size makes it really good for slingers and the natty wood tamas break in really well. I had an Oak Halfsplit and it was really good (oak ken x oak/walnut tama). Currently just have the walnut stripe Flow (maple ken and maple tama w/ walnut pinstripe). The Sol Vibes are standard sized setups. The ken shape is very standard (similar to ozora shape). They're all maple wood setups with silk paint, coming in a number of colors and each designed by one of Sol's current and former players. The paint is super durable, helps with tracking, and plays as good as KUSA silk (my opinion anyways). Currently all are sold out but may be restocked soon. The Sol Pioneers are beech standard setups released a couple months ago. Instead of silk paint, there are only 4 designs available that are all painted in their 'sticky glaze' (similar to Slawdawg Lol Clear). The paint is super tacky out of the box and breaks in for a good slick/tack ratio. They also offer ken only options and full natty options in standard sizes.
I believe my first natty was a sol, one of the best purchased I've ever made. Learned to juggle on the flow.
Yeah I've got a ash cups flow with a mahogany/walnut halfsplit tama, and the subtle size increase is really fun. Slingers are nuts on it too!
My Slice of Paradise Sol Vibe has become one of if not my main jammer recently - I absolutely love it! The shape is pretty nice and well rounded (can't go wrong with Maple) and all the Vibes have really unique and cool color ways. Though I'd say that the paint, while durable and similar in feel to the KUSA silks, is notably slicker/less grippy though. At least on mine. Nonetheless highly recommended! I own a Flow as well, and it also slays.
The sol vibes are great! It's a maple ken so it lasts a long time! The silk paint stays tacky for a long time, and doesn't chip. It's just wears down over time, like most tamas do. And for the price! It's and amazing deal!
The grain on the flows are gorgeous. I'll try and snap some pictures. Also Chad is just a stand up guy who does a lot for the community