Hitting does come out slightly ahead in the rollouts:
  White is Player 2
score: 0 pip: 155  Unlimited Game Jacoby  pip: 159 score: 0
Blue is Player 1  
XGID=aBDaBdEdeB:0:0:1:21:0:0:1:0:10 
Blue to play 21 
1.  Rollout^{1}  13/11 8/7*  eq: 0.000 
 Player: Opponent:  49.59% (G:16.79% B:0.69%) 50.41% (G:15.07% B:1.05%)  Conf.: ± 0.004 (0.004...+0.004)  [100.0%] Duration: 2 hours 23 minutes 

2.  Rollout^{1}  24/21  eq: 0.011 (0.010) 
 Player: Opponent:  49.26% (G:13.62% B:0.47%) 50.74% (G:11.73% B:0.47%)  Conf.: ± 0.004 (0.014...0.007)  [0.0%] Duration: 2 hours 15 minutes 

3.  Rollout^{2}  24/22 8/7*  eq: 0.025 (0.025) 
 Player: Opponent:  48.83% (G:15.91% B:0.66%) 51.17% (G:14.37% B:0.82%)  Conf.: ± 0.008 (0.033...0.017)  [0.0%] Duration: 38 minutes 17 seconds 

4.  Rollout^{3}  24/23 24/22  eq: 0.058 (0.058) 
 Player: Opponent:  48.25% (G:13.25% B:0.48%) 51.75% (G:12.84% B:0.51%)  Conf.: ± 0.015 (0.073...0.043)  [0.0%] Duration: 7 minutes 52 seconds 


^{1} 20736 Games rolled with Variance Reduction. Dice Seed: 90333169 Moves: 3ply, cube decisions: XG Roller
^{2} 5184 Games rolled with Variance Reduction. Dice Seed: 90333169 Moves: 3ply, cube decisions: XG Roller
^{3} 1296 Games rolled with Variance Reduction. Dice Seed: 90333169 Moves: 3ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10
Let's play around a little.
  White is Player 2
score: 0 pip: 155  Unlimited Game Jacoby  pip: 161 score: 0
Blue is Player 1  
XGID=aBDaBdEdeB:0:0:1:21:0:0:1:0:10 
Blue to play 21 
1.  Rollout^{1}  13/11 8/7*  eq: +0.111 
 Player: Opponent:  52.46% (G:17.10% B:0.72%) 47.54% (G:13.87% B:0.88%)  Conf.: ± 0.012 (+0.099...+0.124)  [100.0%] Duration: 17 minutes 29 seconds 

2.  Rollout^{1}  24/22 8/7*  eq: +0.079 (0.033) 
 Player: Opponent:  51.43% (G:16.76% B:0.69%) 48.57% (G:13.77% B:0.80%)  Conf.: ± 0.011 (+0.067...+0.090)  [0.0%] Duration: 18 minutes 08 seconds 

3.  Rollout^{1}  8/7* 6/4  eq: +0.021 (0.090) 
 Player: Opponent:  49.91% (G:16.54% B:0.65%) 50.09% (G:14.23% B:0.88%)  Conf.: ± 0.011 (+0.010...+0.033)  [0.0%] Duration: 17 minutes 55 seconds 

4.  Rollout^{1}  24/21  eq: +0.016 (0.095) 
 Player: Opponent:  50.16% (G:13.65% B:0.48%) 49.84% (G:11.42% B:0.50%)  Conf.: ± 0.011 (+0.005...+0.027)  [0.0%] Duration: 16 minutes 52 seconds 


^{1} 2592 Games rolled with Variance Reduction. Dice Seed: 99493389 Moves: 3ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10
Our position is stronger and we are further behind in the race  any nonhitting play is a blunder.
  White is Player 2
score: 0 pip: 155  Unlimited Game Jacoby  pip: 163 score: 0
Blue is Player 1  
XGID=aBDaBdEdeB:0:0:1:21:0:0:1:0:10 
Blue to play 21 
1.  Rollout^{1}  8/7* 7/5  eq: +0.132 
 Player: Opponent:  52.48% (G:17.29% B:0.66%) 47.52% (G:12.68% B:0.67%)  Conf.: ± 0.008 (+0.125...+0.140)  [99.3%] Duration: 33 minutes 17 seconds 

2.  Rollout^{1}  13/11 8/7*  eq: +0.119 (0.014) 
 Player: Opponent:  52.58% (G:16.64% B:0.66%) 47.42% (G:13.70% B:0.87%)  Conf.: ± 0.008 (+0.110...+0.127)  [0.7%] Duration: 38 minutes 28 seconds 

3.  Rollout^{2}  24/22 8/7*  eq: +0.076 (0.056) 
 Player: Opponent:  51.61% (G:16.25% B:0.59%) 48.39% (G:13.11% B:0.73%)  Conf.: ± 0.015 (+0.061...+0.092)  [0.0%] Duration: 9 minutes 46 seconds 

4.  Rollout^{2}  24/22 6/5  eq: +0.055 (0.078) 
 Player: Opponent:  50.88% (G:14.70% B:0.46%) 49.12% (G:11.85% B:0.45%)  Conf.: ± 0.017 (+0.038...+0.072)  [0.0%] Duration: 8 minutes 08 seconds 

5.  Rollout^{2}  24/21  eq: +0.051 (0.082) 
 Player: Opponent:  50.68% (G:13.98% B:0.48%) 49.32% (G:11.11% B:0.43%)  Conf.: ± 0.015 (+0.036...+0.066)  [0.0%] Duration: 8 minutes 19 seconds 


^{1} 5184 Games rolled with Variance Reduction. Dice Seed: 99493389 Moves: 3ply, cube decisions: XG Roller
^{2} 1296 Games rolled with Variance Reduction. Dice Seed: 99493389 Moves: 3ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10
Same here, except the builder on the 11pt is no longer pointing to an open spot, so it's better to cut down on the number of return shots and create an extra builder for the attack.
  White is Player 2
score: 0 pip: 155  Unlimited Game Jacoby  pip: 155 score: 0
Blue is Player 1  
XGID=BaDaBdEdeB:0:0:1:21:0:0:1:0:10 
Blue to play 21 
1.  Rollout^{1}  24/21  eq: 0.105 
 Player: Opponent:  46.55% (G:13.49% B:0.28%) 53.45% (G:12.88% B:0.54%)  Conf.: ± 0.013 (0.118...0.092)  [100.0%] Duration: 7 minutes 35 seconds 

2.  Rollout^{1}  24/23 24/22  eq: 0.159 (0.054) 
 Player: Opponent:  45.30% (G:13.21% B:0.29%) 54.70% (G:13.53% B:0.53%)  Conf.: ± 0.015 (0.174...0.144)  [0.0%] Duration: 7 minutes 12 seconds 

3.  Rollout^{1}  13/11 8/7*  eq: 0.163 (0.058) 
 Player: Opponent:  45.24% (G:15.67% B:0.39%) 54.76% (G:16.20% B:1.06%)  Conf.: ± 0.017 (0.180...0.145)  [0.0%] Duration: 7 minutes 47 seconds 

4.  Rollout^{1}  8/6 8/7*  eq: 0.170 (0.065) 
 Player: Opponent:  45.18% (G:15.08% B:0.35%) 54.82% (G:15.72% B:0.85%)  Conf.: ± 0.016 (0.187...0.154)  [0.0%] Duration: 7 minutes 27 seconds 

5.  Rollout^{1}  24/22 8/7*  eq: 0.175 (0.071) 
 Player: Opponent:  44.89% (G:14.73% B:0.34%) 55.11% (G:15.09% B:0.82%)  Conf.: ± 0.017 (0.192...0.159)  [0.0%] Duration: 7 minutes 55 seconds 


^{1} 1296 Games rolled with Variance Reduction. Dice Seed: 64669262 Moves: 3ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10
I'm not sure how to explain this one. We have an ace point which should point to attacking game plan. If I have to guess, I'd say it's the noncommitment principle; with better home board points we keep our options open for both attacking and priming games, whereas here hitting commits us to an allout attack and we don't really have enough ammunition in the hood. Splitting back checkers is more flexible. (?)
  White is Player 2
score: 0 pip: 155  Unlimited Game Jacoby  pip: 159 score: 0
Blue is Player 1  
XGID=aBDaBdEcbdB:0:0:1:21:0:0:1:0:10 
Blue to play 21 
1.  Rollout^{1}  24/21  eq: 0.230 
 Player: Opponent:  43.51% (G:10.81% B:0.36%) 56.49% (G:12.63% B:0.54%)  Conf.: ± 0.013 (0.244...0.217)  [100.0%] Duration: 7 minutes 53 seconds 

2.  Rollout^{1}  24/23 24/22  eq: 0.272 (0.042) 
 Player: Opponent:  42.84% (G:11.00% B:0.34%) 57.16% (G:13.50% B:0.54%)  Conf.: ± 0.014 (0.286...0.259)  [0.0%] Duration: 7 minutes 40 seconds 

3.  Rollout^{1}  24/22 8/7*  eq: 0.281 (0.050) 
 Player: Opponent:  42.86% (G:12.28% B:0.47%) 57.14% (G:15.60% B:0.83%)  Conf.: ± 0.017 (0.297...0.264)  [0.0%] Duration: 9 minutes 00 second 

4.  Rollout^{1}  13/11 8/7*  eq: 0.302 (0.071) 
 Player: Opponent:  42.22% (G:12.90% B:0.43%) 57.78% (G:16.20% B:1.11%)  Conf.: ± 0.016 (0.318...0.286)  [0.0%] Duration: 8 minutes 25 seconds 


^{1} 1296 Games rolled with Variance Reduction. Dice Seed: 64669262 Moves: 3ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10
Strengthen white position and splitting of course becomes mandatory.
  White is Player 2
score: 0 pip: 156  Unlimited Game Jacoby  pip: 159 score: 0
Blue is Player 1  
XGID=aBDaBdEdeB:0:0:1:21:0:0:1:0:10 
Blue to play 21 
1.  Rollout^{1}  13/11 8/7*  eq: +0.090 
 Player: Opponent:  51.58% (G:17.99% B:0.62%) 48.42% (G:13.93% B:0.94%)  Conf.: ± 0.016 (+0.074...+0.107)  [100.0%] Duration: 8 minutes 32 seconds 

2.  Rollout^{1}  24/22 8/7*  eq: +0.032 (0.058) 
 Player: Opponent:  50.20% (G:16.48% B:0.69%) 49.80% (G:13.80% B:0.80%)  Conf.: ± 0.017 (+0.016...+0.049)  [0.0%] Duration: 9 minutes 06 seconds 

3.  Rollout^{1}  24/21  eq: 0.049 (0.140) 
 Player: Opponent:  48.30% (G:13.24% B:0.42%) 51.70% (G:12.19% B:0.50%)  Conf.: ± 0.013 (0.063...0.036)  [0.0%] Duration: 8 minutes 13 seconds 


^{1} 1296 Games rolled with Variance Reduction. Dice Seed: 94782038 Moves: 3ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10
Finally, Casper's variant. With a blot on the 8pt being out of the range of the white checker on the ace point hitting is also clear.