Could you beat your current HM POT right now if you ran a HM? The 10 miler is a little more forgiving because in general the shorter the distance the less required endurance to succeed. In general, that's why runners see better conversions between 5k to 10k, then HM to M. Most have the speed but lack the endurance to match the race equivalency. The more focused the training on improving endurance the closer one gets to race equivalency. So a 10 miler is slightly shorter than a HM, thus you are likely to perform better at it (based on race equivalency). BUT, if you don't feel as if you could beat your HM POT next weekend, then the chances of improving your POT via 10 miler is medium-low. If you feel you're in better shape then when you ran the HM POT (and the course/environment is near equivalent), then I say go for it.
When making these types of decisions, I usually ask myself whether this upcoming race gives me optimal conditions. Am I in good shape relative to past performance? Is the weather ideal? Is the course ideal? If yes, then it is likely to be a good full effort race.