Take about 100 rounds each of hot .357 loads (maybe 158s, but I like 125s), some easier .357s (Golden Saber) and some .38+P and .38+P+. What's that--400, 500 rounds we're up to?
If you have a shot timer, great. Even if you don't, load cylinders and shoot on target as rapidly as you can.
If you're like most people, you will notice that it takes you more time to get back on target with heavier recoiling rounds. You may find that some rounds don't pull you off target at all and you can empty the cylinder, all "A", under 2 seconds (world record for 8 shots is 1 second).
You may find that full-house .357s slow you way down. Or not at all.
And you will have your answer. Your answer is yours, for your particular gun. My answer is .38+Ps or Golden Saber .357s. Took me about 5 long days of shooting to get my answer.