The most obvious differences are technical and practical -- not theoretical.
In theory, all you need is twice the energy for every 3db difference. In practise however your 90db spl/1m/2,83V will need 1000W energy to reach 120db spl and will have disintegrated long before those watts reach them!
That's assuming you have 1000Watts available to you, of course.
So, higher sensitivity allows dynamic headroom with reasonable requirements -- say 50-100 watts amplification. Indeed, if you have REALLY sensitive speakers, you can get away with less than 50 watts energy -- much easier to find than 1000!
In theory, all you need is twice the energy for every 3db difference. In practise however your 90db spl/1m/2,83V will need 1000W energy to reach 120db spl and will have disintegrated long before those watts reach them!
That's assuming you have 1000Watts available to you, of course.
So, higher sensitivity allows dynamic headroom with reasonable requirements -- say 50-100 watts amplification. Indeed, if you have REALLY sensitive speakers, you can get away with less than 50 watts energy -- much easier to find than 1000!