With Magus you're stuck in singleton style, and focus almost all of your efforts on making shocking grasp awesome, the sad truth is that most magus builds are traps. EK on the other hand can fight in just about any style, and cast any kind of spells you want. Guns, bows, two handed weapons with power attack, reach weapons, hell and that's just the tame stuff. A properly built EK will end with 9th level spells and a +16 BAB.
EK also has the advantage of being able to combine really weird stuff into weirdly awesome combinations, want to be a triple threat hedge witch/fighter/EK who can spontaneously cast healing spells, want a shield with 0% arcane spell failure, want to add your guns enhancement modifier to your opponents save dcs? The Magus's spell list doesn't even have as many spells as the transmutation school.
As soon as you get into EK (lv 3 or 7) Magus starts falling behind fast, by the end levels when the EK is turning into a giant or a dragon, rocking a 30 something strength with power attack raining maximized empowered fireballs, the Magus is still stuck having to run into point blank range hoping he can crit with his shocking grasp spell strike. Magus is a terrible class for those who want to gish but have 0 patience. Hell I think the arcane duelist Bard archetype does a better job at being a gish in a can than Magus.
