I only have the two rapids, but the design is as follows from best to worst:
Rapid (red) > Rapid (not red) > pro > trigger
I'd completely put uf with the half-backlighting of the pro, as it's much better than the trigger, looks wise.
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As far as half-backlit, I prefer symmetry, but I rather like the thought: It'd greatly help you find your hand to the keyboard during a dark night of gaming.