Talking strenthening knees here....
Recumbent or regular should make little difference, as resistance to pedal stroke is what you're looking for.
Now on the road, recumbants need a big tall flag, so cars can see you.
And normal bikes give a bit of upper body workout, especially the arms when standing up and climbing.
Now recumbants with arm pedal power helps exercise the arms, but then, not the legs.