just for interest - what does it mean for the 750ti cards?
are they work with the cryptonight algo satisfying - or is it senseless ?
i think most of it will be down to how much memory you have available to the GPU. The MARS cards have 3 or 4gb of memory. The 750Ti has 1 or 2 gb, so that may give speed comparison? normally high memory usage algos don't use much processing power