you may be asking the wrong question. If you are doing a lot of strength training and "want to get fit and lose fat" the HRM might be helpful keeping you motivated by giving you some numbers to track, but the workouts themselves are what are going to get you results. You can track the workouts on SP (sets, reps, wts, minutes).
You can also used perceived exertion as a guideline to how hard you are working out, instead of a HRM. Aim for a perceived exertion of 7 to 8 on a scale of 10, 14-16 on a scale of 20.
If you are on certain medicines, they can affect your heart rate and therefore make the HRM inappropriate for your workouts.
That being said, if you want to lose excess fat, you HAVE to watch your nutrition and do some cardio.
Best of luck with your decision.
The turtle only makes progress when it sticks its neck out. -James Bryant Conant
It's easier to hit your target when you know what you are aiming at.