Hi. I need some help.

So Ive got three ideas for my first full length story. Im going to put a ton of work into one of them but i dont know which. I was wondering if some kind people could voice their opinions on whichever one seems more promising.

Story 1:
Genre: Fantasy
Note: This story is set in a modern world of magic, where a few people have magic powers which are closely regulated.
Plot: Two brothers are orphaned, one of them aged 5 and the other age 7. They are taken into a rich family who have a 5 year old daughter. The older one becomes emotionless, withdrawn and quiet. The younger becomes optimistic, happy and playful as he quickly befriends the familys daughter. The two become romantically entwined over time.
However, someone who works for an anti-government organisation goes on a rampage one time, and despite the authorities best efforts to stop them, they end up causing a ton of casualties. At this point the older brother is 19, and the younger is 17. One of the casualties was the girl who the younger brother was in love with. His optimism and hope is crushed cruelly, and he sets out to use his magic powers to destroy the group who killed her, by using any means neccessary.
The older brother, upon seeing the lifeless corpse of someone he considered a sister, realised that his actions were childish and stupid, realising that caring is better than hating the world and keeping to youself. He decides to try and stop his younger brothers murderous rampage, but he has no magic powers. He is a brilliant strategist though, and the climax would be the two having a final bout, leaving one dead probably.
Ask any questions you want about the plot - I may not be able to answer them all but ill try.

Story 2:
Genre: Crime
Note: Takes place in a modern setting
Plot: A brillaint private detective harbours a secret life of murder because of a religion he follows. Another, equally brilliant private detective is alerted to the possibility that he is a murderer, and is sent to gather concrete proof.
Meanwhile, someone suspects the 2nd private detective of doing crimes of his own, and sends the first after him. Its a cat and mouse style book which follows each gathering the evidence needed to take down the other.
Each discoveres that the other is trying to follow them around halfway through. Ungency is added, because the one whose crimes are proved first will get the death penalty probably, and the other would go free.

Story 3:
Note: Medieval style setting. Magic is rare and inhibits humans or objects at random. These people are revered in society as demigods. One of these people becomes a commander over a small area of land. To make a point about how serious he was, he decided to personally execute a family who couldnt pay their taxes on time. One of the children avoided execution because of a man his family helped out - the reason they couldnt pay their taxes.
His anger gives him a single, clear goal - kill the commander and any other corrupt people working in the Government. He gets trained by an ex-night who left after challenging the commander. The child develops, and when he is a teenager he discovers his magical power to stop time. He forms a group to help him kill the corrupt and ruthless commander. He knows that he cant take down the regime and army with a small group, and expands it, becoming the largest criminal group in the country - The Rogues.