I have an R2 Saji gyuto, but no experience with the others. I like the knife, but it needed a bit of work out of the box (the front half of the blade was significantly thicker behind the edge than the back half; spine and choil not rounded). Ideally this was just an isolated case, but if you do purchase it, I would ask Koki/Mari for an inspection prior to shipment.
The blade profile is pretty flat, spine is thin (just a bit over 2mm), the blade is pretty tough (compared to the other powdered steel knives I have) and edge retention seems to be very good (it went through 7 months of nearly daily home use without sharpening or stropping). Stiction isn't a big issue with my knife; wet potatoes might stick to the blade but they're pretty easily removed (I've had some other knives where they were essentially glued to the blade).
If you get the deep etched damascus iteration of the knife, you might notice that the cuts don't feel as smooth as they usually do. Personally, I didn't like this and polished it to a near mirror finish.
If I were to go back, I'd probably choose the Tanaka based on Theory's videos and Tanaka's reputation for making very good cutters.