Pros
There are limitless opportunities availible in the Marines. Whether it be getting job skills for the future, or college opportunities, a chance to gain leadership experience, the list could go on forever! The leadership in front of you has "been there and done that", so you know that when you have to do something they aren't just telling you to do something they wouldn't think of doing. The senior leadership in DC cares for the lowest man just as much as the supervisor just in front of him. When outperforming your peers, you are rewarded for it in the means of promotions and subsequent pay raises. Overall a great organization to work for.
Cons
If you are planning on making a career out of the Marines then at some point you will have to move. This means packing up your family and all of your belongings and moving across the nation or possibly overseas. To some this may not be a downside for those that like to travel that is. Depending on the work tempo family time may be severely outweighed by time at work, this is usually balanced out by extra "long weekends" and time off. This is, however, not always the case. Upon sucessful completion of a job or "mission" there isn't always that reassuring "pat on the back" or "good job" which sometimes helps provide the motivation to keep rolling to the next task.