It isn't obvious and you also have to add the weight and the parasitic draw from the SC. Especially with the MP45, as it's too small and too easily heat-soaked to make any more power, tune or not. LionZoo has the Elise SC and has considered removing the SC. If that's not a non-endorsement of the MP45, I don't know what is. If you haven't read the other posts in this thread, you should.
yeah the MP45 supercharger doesn't move a whole lot of air compared to the others as its smaller. I will soon be finding out (tomorrow as matter of fact) because I've had one put in my n/a 2005. In my case in addition to a one-off custom ECU tune, also have performed lot of head work (porting an polishing) and also on in the intake,bigger injectors, etc....and I had previously upgraded the cooling system (radiator and fans) along with a bunch of other stuff. I assure you that I'm waaay beyond the 220hp - 240hp normally seen with the MP45. For most people just getting a REV300 would be a simpler way to get the power (and probably cheaper in the long run due to the head and intake work) -- but I got a screamin deal on the labor and ECU tune
Now if you're just going to have the stock MP45 setup - it might be a little bit quicker, the driveability might improve some due to the extra torque - but "worth it"? I guess that depends on the individual and how much money they wanna spend and how fast they wanna go. I have heard so much from both sides of this -- lots of guys have told me that the mp45 supercharger makes all the difference in the world - and others have said it's not worth it.