Player B is more clutch because he helped his team more. He Two singles and eight inning ending strikeouts are better than eight inning ending outs, no matter how weak player B's singles were or how hard player A's outs were hit. Clutch is about what happened. Given the difference in luck, one could logically justify taking his chances with player A in future clutch situations, but in that scenario, player B was more clutch.
Here's a handy device for determining clutch impact through Win Expectancy and Win Probability Added.
www.hardballtimes.com/thtstats/other/wpa_inquirer.php
The run environment is limited to steps of half a run (3.5 runs, 4, 4.5, 5), and when dealing with hypotheticals, you have to make your own judgement on how far someone on base advances. Nevertheless, it is very helpful in showing how different events change the odds of winning a game. Remember that it is set from the home team's perspective, so if we assumed both players are on the home team in each situation, you would want it set to bottom of the ninth, lead -1.