Damn good question. Although I rarely take the payout until the lines has moved a huge amount, I always think about it for a second when it comes up.
If you're looking at win %, that might be estimated by looking at what the long-term resuts are for the given odds on an implied probability table (e.g. if the odds on the bet were -160, the estimated hit rate is 61.53%).
If you're looking for unit return, that might be impossible to accurately find since the cashouts offered usually change as the line moves making it tough to track and compile accurate info.