I have never seen a Sparrowhawk in the skies since 0.3.
I have, yesterday.
Too bad I was in a Huit P and it was passing 400m away from me

But let's look at the Sparrow variants for a second:
Prime:
2 AC2, 2 MGun
8332 CBills
A:
2 ERSBL, 2 MPL, C3
17164 CBills
B:
2 MGun, 2 SSRM2, BHP
10914 CBills
C:
2 MBL, 2 MGun, NARC, BAP
18414 CBills
No variant has any tons for extra ammo, they all have paper armor and it's not even faster than a Sulla.
When flying level, the Sparrow goes up to ~360kph, ~410kph with boost, the Sulla does ~350kph, ~420kph with boost.
What are they good for?
Prime: Hunting other Sparrows/Harassing Sullas?
A: Pitiful scout, can try to attack flyers/ground targets but the 400m max range means it's probably going to die
B: 2 SSRM2? I don't know, tickle VTOLs?
C: NARC stuff, try to do damage with it's MBLs
It's obvious and understandable that the Sparrowhawk doesn't have alot of tonnage for weapons, but about the only thing it has going for it atm is that the Prime is the cheapest vehicle available and can therefore be used as throwaway transport. Hop in, bail near a base, cap it, buy something that can actually, you know, do stuff

A variant with C3 and BHP, maybe NARC but no other weapons would be a great fast scout and as long as the ClanVsIs balance isn't complete and the mode viable, the Sulla is just better at everything.
If the Corsair is going to be similar to the Sulla, the Sparrowhawk won't ever be used unless someone just wants to give all his remaining cash away and move out to get himself killed >_>