The difference is enlisted is going to be more like 18 year olds that join for various reasons (at least in the Army, which is my experience) are going to be privates and work their way up, or do their 3-4 year commitment in a specialty field they choose. So enlisted people choose "Hey, I want to be a satellite systems tech or 25S, (read, not a grunt) so off to fort gordon you go to learn about satellite transmission systems or I want to be an 88M (light wheeled mechanic) or I want to be an 11B (infantry)." They go to a recruiter, get the contract they want, then off they go to basic training.
ROTC is an Officer Training program, where you go in as an officer, which typically, depending on where you're assigned, you'll have 24-28 people assigned under you directly out of college, if you get a platoon leader slot. Great for a resume.
I did a little bit of both, Joined the Florida National Guard and did Infantry Basic (OSUT) and came out an E3, then did the Cadiot route through ROTC. Payed for College and then lived in Germany for a few years before getting out.