I just watch Ed O'Laughlin make the correct play at DMP in a similar situation. He was far enough ahead in the race that it was clearly right not to hit. Hitting leaves repeat shots, of course, and that is the reason not to hit. However, if the race is wovrse, hitting can be very right.
The position below is the tipping point...change the race either way and you change the play. How do you know, over the board, how much worse off you have to be in the race to warrant the hit? Does anyone have a formula or is it pure guesswork?
  White is Player 1
score: 0 pip: 58  1 point match  pip: 42 score: 0
Blue is Player 2  
XGID=CDCBBbAbdcd:0:0:1:61:0:0:0:1:10 
Blue to play 61 
1.  Rollout^{1}  6/Off 1/Off  eq: +0.516 
 Player: Opponent:  75.78% (G:0.02% B:0.00%) 24.22% (G:0.00% B:0.00%)  Conf.: ± 0.001 (+0.514...+0.517)  [72.5%] Duration: 1.0 second 

2.  Rollout^{1}  6/5* 6/Off  eq: +0.515 (0.000) 
 Player: Opponent:  75.76% (G:0.91% B:0.02%) 24.24% (G:0.00% B:0.00%)  Conf.: ± 0.001 (+0.514...+0.516)  [27.5%] Duration: 1.7 seconds 

3.  3ply  6/Off 3/2  eq: +0.420 (0.095) 
 Player: Opponent:  71.02% (G:0.02% B:0.00%) 28.98% (G:0.00% B:0.00%)  

4.  3ply  6/Off 2/1  eq: +0.402 (0.113) 
 Player: Opponent:  70.11% (G:0.03% B:0.00%) 29.89% (G:0.00% B:0.00%)  

5.  3ply  6/Off 4/3  eq: +0.401 (0.115) 
 Player: Opponent:  70.03% (G:0.02% B:0.00%) 29.97% (G:0.00% B:0.00%)  


^{1} 1296 Games rolled with Variance Reduction. Moves: 3ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10, MET: Kazaross XG2