New to this and need to find a good HRM or fitbit ?

I have a Fitbit One! I also have a HRM. I love them both and couldn't imagine not having either one. The fitbit is what started my weight loss journey 2 years ago. The fitbit does track calories but I find it sometimes underestimates when I compare to my HRM for the higher intensity workouts. With cycling the fitbit tracks the movement (at least for me because I wear it on my bra and my boobs move when I bike. But the HRM would be more accurate in it's tracking. For classes that don't involve a lot of back and forth movement like yoga or weight lifting where you are moving but you are mostly in one place, the fitbit would not be able to track your calories as well because the fitbit takes into account steps and number of steps per minute to get the calories burned number.