No, the risk/reward is not the same. The risk is the same (I would argue that the risk was higher on the FG, since we're less likely to hit a 47 yarder than to convert a 4th and 3 with this offense, but for the sake of this discussion, we'll say they're equally likely). However, the reward for making the 4th down is that the game is over. Florida was out of timeouts There was about a minute left. Tennessee takes 2 knees. The reward for hitting the FG is that UT is up 14 and is kicking off to Florida. Florida can still get a quick score, get an onside (which they did) and have a chance to tie and win in OT.
The reward for making the 4th down was much higher...basically, a win. The reward for hitting the FG is making a win highly probable, but far less definite, especially with the way our secondary was playing. Coach made the right call, it just wasn't executed.