To clarify a bladesinger has better AC than a Druid in every fight and can have the highest AC in the game multiple times a day (to be specific twice at levels 2-4, 3 times at levels 5-10, 4 times at 9-12, 5 at 13-16, 6 at 17-20). Further they can give their opponent disadvantage for most fights with a second level spell (or a first level spell if fighting a fey, fiend, celestial or undead) meaning not only do you have to roll high to hit, you have to roll high with disadvantage.
Even out of bladesong and with no magic items a 4th level bladesinger can push AC to 22 using point buy (13+4dex+5shield spell). Go in bladesong and it is 25, and you are rolling against that 22/25 with disadvantage most of the time. With their unique extra attack feature, a bladesinger after level 6 will do a lot of damage also outrunning most classes in the game in terms of melee damage with one-handed weapons. A few heavy weapon builds will outdamage bladesingers and high-level fighters with 3+ attacks will as well but not with a comparable AC.
At any level a Bladesinger is more than a match for a Druid in melee and after level 6 a bladesinger would more often than not beat 2 Druids simultaneously.
That is a completely absurd claim.
First, Bladesingers won’t reliably have Bladesong up in any campaign I’ve been in, until around 11th level, when most campaigns are done or ending. At low level, they have it 2/day.
Secondly, Shield costs a spell slot and lasts
at most 1 full round. So no, their AC isn’t reliably that high. And I don’t know how you figure attacks against them will reliably be at disadvantage. You’re gonna need to back that one up.
Third, they still have garbage HP, lower attack bonus than the Druid, and no particular defense against things like Call Lightning except mitigation via more spell slots, which Druid also has, and the BS
has no self healing.
And the Druid doesn’t need to go MAD as badly as the Bladesinger does, so the Druid is going to resist things like Hold Person more easily.
Any Druid subclass could gank a Bladesinger, unless the BS hides behind some summons and acts like a normal Wizard, in which case they’d be better off as an Abjuration Wizard. The only subclasses BS can stand up to reliably are the melee subclasses, and the Druid is still gonna win 7 or more times out of 10.
The BS if fun. It’s not in the top tier of any category but AC, though, and even that is situational.
Now, MC builds using Bladesinger can’t be really powerful in melee, as long as you don’t mind losing out on greater magical power overall, (and I wouldn’t. I signed up to play a gish, not a mage), but then so can Druid MCs like taking Beastmaster Ranger (with Tasha’s options) or Monk (all your monk stuff works in wild shape RAW) or War Cleric, or nearly any Fighter.
But single class? Druid wins.