My friend, this is a very nice question. Where did you find this formula?
If my memory serves me well, i have seen such a similar parameter in Andrei Fomin's book "Flanker Story".
There was a diagram where the Specific Excess Power (SEP) was divided by the aircrafts' total projected area. I think this is the Sal in your formula. That was making sense, since the biggest the frontal projected area, the biggest the power required to "move" it.
I'll check again in the book for the SMQ parameter. But no matter what it is, keep in mind this :
Since the Thrust parameter is in your formula, the SMQ varies according with altitude and speed.
A turbofan, like the AL31 or the F110 has a greater by pass ratio than, say the F119 or the F404, therefore, subsonically and at low altitudes are performing better than supersonically and at hi altitude.
What i am trying to say, is that a fighter X may have a better SMQ than a fighter Y, but under another set of conditions, this is very likely to change.