The main line of the Scotch Gambit is often referred to as Modern Attack which actually transposes to the Modern Variation of the Two Knights Defense (aka Dubois-Reti Defense). It seems like a rough fight for both players until one of the sides usually makes a mistake and goes down in flames.

4. ...      Nf6!

5. e5!    d5

6. Bb5   Ne4

7. Nxd4 Bd7

8. Bxc6  bxc6 (8... Bxc6?)

9. 0-0    Bc5

10. f3    Ng5

11. f4    Ne4

12. Be3

This is arguably the best choice for Black to slow down White's development and get some counterplay. However, if Black doesn't play accurately enough their mistake may even lead to quick mate. That is why, I personally prefer to play the Scotch Gambit as White.