The answer is:
Not very.
The Eldritch Knight is a start - but he's not really a Fighter in any meaningful sense of the word. He's more like a Ray Spell specialist.
In order to qualify for Eldritch Knight you need at least 5 levels of Wizard and one level of a Warrior class (Fighter, Barbarian, Paladin, or Ranger).
Then you get one level where you get a Bonus feat and a BAB, and no spellcasting, and then the entire rest of the class is gaining spellcasting and BAB. Throughout the whole time you are in the class you are getting d6 hit points.
But the thing is, a d6 hit points and a BAB isn't advancing like a Fighter - it isn't even advancing like a Warrior.
At 12th level, you'll have a Caster Level of 10, a BAB of +9, and 43.5 hit points (plus 12 times Con Bonus). You'll also have 2 bonus feats (or one bonus feat and the first level bonus of some other fighting class) - but for fighting purposes that's going to be largely subsumed in the fact that you are short one magic feat over a Wizard and will in any case want to pump up your wizarding with at least two of your normal feats.
So really, you fight like a 12th level Aristocrat, at best. A 12th level Aristocrat has no bonus feats (but can spend them all on fighting, so he's got at least as many combat feats as the Eldritch Knight), a BAB of +9, and 57.5 hit points (plus ten times your Con Modifier).
And you cast magic like a 10th level wizard. You are down one magical feat for not having level 10 in wizard, but you got an extra feat at character level 12 to make up for it.
So a 12th level "Eldritch Knight" has the choice to fight like a 12th level Aristocrat or cast magic like a 10th level Wizard. Or you could be a 12th level Aristocrat, and take the Leadership feat and be followed around by a Wizard two levels lower than yourself.
Better yet, you could take 12 levels of a Player Character Class and still take Leadership and be followed around by the 10th level Wizard.
And unfortunately, Spellsword and Bladesinger aren't even that good.
-Frank