I haven't shot any benchrest in a while but photography has been one of my principle hobbies for a couple of decades. There are obvious parallels between scopes and camera lenses.
Before you go looking for high levels of magnification, a prime characteristic of your scope optics should be "resolving power". Boosting a scope to look at features near to or exceeding its inherent resolving power just gives you a "muddy" view. Resolving power is determined in optical physics having to do with the lens design and the optical quality of the lenses. Optical reality is that it is inherently easier to achieve any given level of resolving power with a fixed design. This isn't to say that there aren't well designed variable lenses/scopes that out perform a cheaper fixed. But the designer has to work to do it, hence $. Lenses with very high resolving power have two characteristic in common, they are fixed and expensive. If I were a scope designer for a, say, 40X scope, I don't think I would spend the necessary money to design for twice the resolving power needed for a 78X. It's a very competitive market and only a small fraction of the market for a scope would thinking about boosting.
In the camera world, "ultimate" sharpness (aka, resolving power) is found with expensive fixed lenses.
I think it's plain that any fixed scope operating at its designed resolution is going to be optically superior to a scope that has been boosted to reach that same resolution.
Below is a shot I took with one of those lenses. (click to expand)
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