Using runs created, the margin values for an average team (i.e. neutral contex)
HR = 1.62 runs
SB = 0.161 runs
CS = -0.391 runs
17HR * 1.62 RC/ HR = 27 RC
60 SB * .161 RC/SB = 10 RC
Of course in SB/CS RC are earned (or lost) on defense while HR RC are earned on offense. So in order to figure this properly both players would have to have the same number of PA and both would bat in the same (or similar) line-up spot. I am also assuming that the 17HR and 60 SB are according to performance history and this is an $80M OL team (or equivilent).
Assuming the above, the decreased defense on average would be easily worth it. But let's face it, you don't build a team to beat an average team, you build a team to beat a variety of specialists ( the HR team, the dead-ball team, or the speed team). And if happen to face an Astrodome/Speed Team in the playoffs, the marginal difference between an A arm and and A+ arm will kill you more than that HR bat could compensate.
Still that being written, the difference in value, 20 runs (I'm guessing the guy with the worse arm actually get more CS) or close to two wins, is too great to ignore. I'd go with the HR hitter (catcher B), especially since Ithink the difference in arms is only A+ to A++ (or perhaps A to A+).