Fouga,
If the choice, regardless of cost, is Hawk or L39, its the Hawk any day.
There is however a huge difference between shooting something down and intercepting it. Interception allows for indentification and confirmation of threat. If you just want to shoot something down then just buy SAMs as earlier proposed.
The average airliner now cruises at 35,000ft and mach 0.85. The fastest, the Citation X, cruises at 0.92. I would love to think a Hawk from a standing start could intercept one but I find it highly unlikely unless the target is comimng toward the interceptor.
The Hawk 200 is also the only version with Multimode radar and is a single seater, therefore no other possible use when not on QRA.