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When I first learned on various sextants, I took to the split mirror design based on the advice of the time about low light/contrast level sights, etc.

When I got my Astra III it came with the standard 3.5 x 40 scope.  This presents the classic split view.  This summer, I purchased the 7 x 35 prism scope to assist with Lunars.

Results were excellent, but I found the switch back to a whole horizon view created by the optics disconcerting at first. I kind of liked the classic split mirror simplicity. I understand this visual change to a complete view to be the result of images superimposed within the scope by the prism arrangment and focal length..

Does the prism scope full view remove the benefit of the split mirror on low contrast marginal sights? 

I understand the light gathering ability of a telescope increases with the size of the aperture, but that percieved visual brightness is quartered by doubling magnification.  This would intially make me think the split still put less in the way of the light and it may be a help.