Ok first thing first. Forget the aspect of letting down people because when you make descions in life not everyone is going to be happy with your descions, so get use to people looking unfavourably or being disappointed at the descions you make, because only time can tell if you made the right one.
I do believe your happiness plays a significant role in what you want to do, after all if you are a successful person and unhappy is the success really worth it?
I honestly think your worried about making the descion because your afraid that the descion you make might be a mistake or the so called wrong descion. But hey everyone will make mistakes so don't be afraid to choose one and go at it with your all
What you could also do is talk to the people in the particular fields you are interested in and see the long term benefits and see which one you would like better in the end( don't only talk to the succesful people talk to the people that haven't been so successful as well, who knows maybe your feelings might lean towards one )
Then based on your feelings towards them after that make a descion but make sure at the end of day that you can stand back and say I'm happy with the descion I made.
