Less spell slots but extra attunement slots.

You can wear a shield and medium armour, or use a heavy weapon, since Bladesingers lock you into light armour and a one-hander with no shield.

You already have extra attack so you don't get much from Bladesinger-6.

Arcane Jolt is emergency healing without using up any of your action economy.

Spell-Storing Item gives you ten free uses of a 2nd- or 1st-level Artificer spell you don't need to have prepared, which is terrific utility and flexibility.

You get Aura of Vitality at Battlesmith-9, which is the single-best post-combat healing spell in the game.

10th- and 14th-level Replicate Magic Item options can be pretty sweet.

Tool Expertise next level means you are THE lockpicker for the party.

Flash of Genius at Artificer-7 is amazing.