I guess the cons would be:
- You wouldn't be able to play defense (if you enjoy the defensive side of things)
- You wouldn't have access to upgrade Recruiting or On the Field skill trees, you could only upgrade Offensive Coordinator skill tree. Which could suck if you want to increase the points you have to recruit with or work up to the insta-commit skill
- Can't play any Special Team plays (Kickoff, punt, FG, extra point), which sucks because sometimes the CPU randomly misses extra points and easy FG's you could have easily made yourself
Pro's:
- If you don't like playing defense, you ONLY can play with your offense.
- The game go by much faster because when on defense the system Sims for you. Thus allowing you to play through seasons quickly, if you have a prized recruit you want to use
- You can recruit just like you were a head coach, you just won't be able to increase your recruiting skills until you become a HC
Those are just a few major ones I can think of, but I'm sure everyone has their own opinions and could add more...