If you are using A14 pistons, in an A12 block, with the A12 crank, you will need A12 rods with the larger wrist pin hole. This can be done by

A. Boring the A12 rods
B. Using the A12a rods
C. Using A13 rods [the 76mm bore version.]

If you are using A15 pistons in an A12 block with an A14 crank, you will need A12 rods with the larger wrist pin hole. This can be done by

A. Boring the A12 rods
B. Using the A12a rods
C. Using A13 rods [The 76mm bore version.]

There is no reason to assume that one engine would be any more reliable than the other, although the longer stroke engine would develop more torque, so would need less flogging to return a given level of performance & the lesser flogged engine should live longer. At least, thats my version of the story.