1) Sure; why not? Once you have Summoning (the technology), I think that Summoning is the most powerful trait in the game. It allows you triple the number of expendable units. Obviously, until that point, Philosophical is stronger.
Without question, Philosophical is stronger for the tech rushing early-mid game - Summoning requires a while to hit, and Philosophical can give you a HUGE early edge. I wasn't doing this until recently, so I didn't get it, and I'm sure I still lack a lot of understanding. Tech pops are the way to go, early.
Philosophical has additional internal synergies with a GP strat due to its ability to speed production of the early buildings allowing more sages, and it also makes some of the most expensive civics you're likely to use free. It is the most powerful trait in the early game because it gets you to the middle game faster than anyone else, likewise speeds the middle game substantially, and is still quite helpful in the late game (if you've bulbed all the techs you want and have academies in your major research cities, a great sage super specialist with library, academy, and crown is nothing to sneeze at).
In contrast, summon gives you longer lasting summons, which lets you have more. If you're rushing summoning, then when it hits, it is savagely strong. It doesn't stay that way, however. It gives a massive spike in power for a while, and then the fact that your summoned troops aren't gaining battle experience takes their short lifespans/high numbers from a high point to a liability. This is a pattern seen throughout the game.
There's a lot of times when particular civs spike in power. Sheaim require the Summoning trait to make the Summoning tech dominant. Vampires become dominant (without cost in traits) once they hit Feudalism. Amurite mage rushes (facilitated through Dain/Philosophical) can come a LOT sooner than Sheaim conjurer rushes, and fireballs will definitely get the job done in the early game. The Hippus will Pillage you from one end to the other incredibly early with their Horsemen if you're unlucky enough to start out next to an angry Tasunke, and once you're pillaged out you're next to dead. The Elven Kingdoms under Amelanchier become nearly impossible to assault once they are covered with Ancient Forests and inhabited by invisible treetop Rangers with poisoned blades. Loki will peacefully convert nearly a whole AI civ for you in the early game without even declaring war. Wood Golems are more or less unstoppable when they first arrive on the scene. The prevalence of wolves in current editions makes the Clan of Embers worg spam horribly dominant from year 1.
I'm not saying Summon/Summon isn't powerful, but I don't see that it is out of line with these. And it comes at the cost of a trait.
Daladinn - my point in bringing you up was that you are not a good example for how most people play and shouldn't be taken as a pro or con of a particular race or strat. I think your response proves that. I assume the victory tool of your strat is to mass spam Chaos Marauders and fireball Witches through Planar Gates?