As one who went away to mesifta/yeshiva at age 14 and who sent his son away at the same age (to the same place), I can report that there are benefits to doing so. I have found that there were fewer distractions OOT. It is easier to concentrate on learning and shtayg away from the familiar distracting home dynamic of travel, outside interests, etc.
That is not to say that there are no difficulties with living in a dorm. While the rebbeim and mashgichim supervise the boys closely, ways can still be found to go outside the box, as it were. For instance, I learned to smoke in yeshiva. Also, dorm life has it’s tests and dangers that bachurim have to learn to avoid.
Sending your son away requires that you know and trust your son. In my experience, the benefits clearly outweighed the drawbacks.