http://www.stavatti.com/SM-27J_H2H_A-10A.html
hmm according to that the SM-27 has a few disadvantages
for starters single engine means you lack in flight redundancy which could make the difference between getting home
secondly its maximum warload is lighter than the A-10 10,000 lb compared to the A-10 16,000 lb
but it is better on range, speed and fuel burn.
to me the SM-27 is a better rapid response fighter and general ground support craft patrolling a battle line answering general calls for air support.
the A-10 with its speed and range disadvantage needs a little more planning to employ which combined with its superior warload makes a great first strike craft also the second engine means you can drop it in a zone with more intense anti air and if one engine gets hit you have a higher chance of getting home.
basically if you have both available the A-10 helps the ground troops take an area and the SM-27 helps hold the area