Any time you can run wires/cables etc. inline with existing objects like motor mounts, the less you need to reach through a web of wires to perform maintenance.
My cables from the alternator and starter, were ran down the alternator side of the pan bolts to the motor mount and then split up according to where they were headed following the motor mount tubing.
Later when you go to change the oil filter, time a mag, work on prop gov or vac (ugh!) pump, you will appreciate the extra clear space. Put in the extra time now, and be rewarded every time you go to work in there.
This applies to everything that you add to the motor that must reach the firewall except your throttle, mixture and prop cables. Fuel lines are usually low enough to be out of the way. But think about them also. It's all about gaining access in the future.