[wILLk0r3 818]

I think it's best to install anything/everything you can to the internal storage, most especially programs that involve constant system access or programs that involve registry tweaks or system settings etc. You can usually get an idea where to install by what you're installing. If installed to a memory card, I would still erase the folder and re-install with a hard reset to avoid any complications when you least expect it. I personally store everything on the internal storage since we have alot of space, and even though I've got ALOT of stuff installed, I still have alot of free space and my device hasn't slowed down at all.