Better a little loose than a little tight, but make sure you actually only have .010- more than that and I would work on tightening it up

I don't focus on rod length more than, as Joe put it, the longest (readily available, reasonably priced, and strong enough) possible, without making a crusade out of it. To put it very simply, a longer rod (which is closer to parallel to the cylinder all through the cycle) transfers energy to the crank, with a little energy pushing out against the cylinder walls due to the leverage. A shorter rod, with greater angularity, pushes against the walls just a bit more- very little, but a bit- so a (very) miniscule amount of power loss and additional wear and tear is just logical- but it would have to get to a pretty severe angle to be worth worrying about, and in the average range of rod ratios, probably not enough to notice or measure. So I go with the longest readily available and proper strength part that will fit, and don't spin about it any more. The 4.25/ 6.7 is a well proven combo that works pretty well (as is the 3.78 or 3.98/ 6.49), and the price is right- move on to @.050's and LSA's where you can REALLY fuss and spin LOL
I see examples of this every day at work, where we use large excavators, CAT 345's and 330's, and most everyone prefers a "long stick"- no pun intended- which is the vertical part that hangs from the boom- the connecting rod between the boom and bucket, as you can just reach farther and do more work with it. A "short stick" will "crowd" stronger horizontally, as in digging and loading the bucket, with more severe angularity (leverage)- like pushing against a cylinder wall. A long stick loses a small amount of horizontal strength, or crowd- which is good in an excavator, but wasted energy in an engine- as in pushing against the cylinder walls. Funny thing, the long stick and short stick lift the same amount of weight vertically- one can nit pick the slight difference in weight of the long stick (or connecting rod) but the total lifting work produced is still the same