Pindle will usually only drop 1 item, or a few potions, or some gold.
Mephi will usually drop 3-6 Items
Plus his council guards will usually drop 5-10 item between them.
Therefore if you do 1x pindle run then you will likely just get 1 item.
If you do 1x Mephi run then you will get about 4-7 semi useful to useful items. (small charms with decent mods, flawless gems, full rejuv potions, maybe useful exceptional , elite, or normal gear.
However,
Mephi is restricted to Weapon and Armor 78.
Pindle can drop Weapon and Armor 81/84/87
A sorc, or any other teleport character can probably do Mephi in 5 minutes, a character without teleport may take 15 minutes.
Pindle can be done in a minute flat, however if you make 5 games in 5 minute u will likely get kicked off battlenet with a realm down.
Therefore, on average you could probably do 5 pindle runs to 1 mephi run
5 items with possible higher levels Vs 4-7 items with slightly lower levels.
In conclusion it comes back to personal preference - if you dont have teleport do pindle , but do Shenk as well, just so u stay in the game for a couple of minutes.
If you have teleport do both pindle and Mephi.
With MF, the main thing to note is that it can be boring, and is very grinding, so break it up and do a variety of Level 85 areas to keep it fun.