If you find both themes okay, how do you implement it? Is it provided by the internal tool builder or do you set it up with hand code?
Some apps that I use, I don't care if they are Light-only. There are others that I only use at night, but are blindingly bright and have no dark option. Conversely, dark themes can be very difficult to see in the daytime.
You'll have to assess when & how your users use your app