I’d say the reason for a flat back is to be able to work off the bur raised by honing the bevel. If the back lets you do that, it’s flat enough. If you only work with stones and no strop, you probably need a flatter back because any irregularities at the edge can keep the edge from reaching the stone. On the other hand, if you use a strop, the tool can be pushed down into the strop and this lets the abrasive reach an imperfect surface. Some people say a strop rounds the edge so the edge can’t be sharp, but they don’t realize that, as long as any possible curve introduced by the strop gives a clearance angle for the work to be done, you will have a sharp edge _and_ you will have the advantage of being able to sharpen an imperfect back. If you’re a total bonehead about it, yeah, you can dub over an edge on a strop, but if you know what you’re doing, a strop is the sharpening tool that saves you from needing perfection. One of the problems with the cryogenic steels, like A2, in my opinion, is that they are too hard to abrade quickly enough with a charged strop, so either things take a long time or you are forced into a flatter, “keep it perfect,” back and working just with stones, likely waterstones because of the high amount of abrasive they contain.
If those observations are correct, and one is prepared to invest time in preparing the tool for use (obviously requiring the knowledge that the tool is not ready for use), then the choice comes down aesthetics, ergonomics, robustness, and edge properties. The first two are in the eye and hand of the user. The latter two can only be appreciated from various subjective anecdotal data, which often seem to be of conflicting nature, perhaps making it difficult to estimate the relevance of the price of the tool. Alternatively, one can go for products of established “ready from the box” quality, possibly having to yield a tad on how they “feel”.