3.35" or 4" 1913 Picatinny Rail?

All, I just bought a new Wildcat .25 MKII and am about to put a bipod on it. I like both the Atlas BT10-LW17 and the BT46-LW17 but will likely go with the BT46-LW17 for a number of reasons (non rotating legs etc.). My question is, what are the pros/cons of the using the 3.35" Picatinny 1913 rail vs. the 4" Picatinny 1913 rail? Is one recommended over the other for the Wildcat or does it matter? Thanks in advance for the advice! -Dave
 
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Here's my Wildcat with the 3.35" rail installed.