The feats are not a good idea for comparison because then I can give the Conjurer two different feats (she has no need for them after all) that make her massively more powerful than the Evoker, and then we'd have to decide whether it was just because of feat choice (I've been down that road before). In reality, taking Spell Penetration and Greater Spell Penetration in a game with Orbs is idiotic because you can save two feats (a massive savings, since Spell Penetration and its Greater cousin tend to be taken using high-level feat slots since they don't help much at low levels) for a BETTER benefit by just casting the Orbs instead. With Orb average damage, if the rest of the party is doing anything, the dragon is dead by round 2 of attacks (and this includes the 15th-level Conjurer vs the vastly stronger Dragon, the Orbs are just that powerful). The damage is already around 25% of the dragon's total per round for the Conjurer only.