For me it's a matter if I want to run my Slann in temple guard or not. Wandering Deliberations gives a lot of low cost spells that don't require a lot of dice, meaning less double 6's and happier temple guard. Focus of Myster gives Lore of High Magic that has a few high cost spells that can be switched over for low cost ones, but still will require you to fire a lot of dice at them... meaning less happy temple guard and you should probably run solo.
