I enlisted in the reserves 5 yrs ago with the intention of going the PCL route. I was told I would miss "at most 1 semester of college" I ended up missing one full year b/c I had a 3 month wait for the new MOS class to pick-up that the recruiter failed to mention, and I had difficulty getting into PLC because I was a reservist will a high probability of being deployed. OSO's will have a hard time taking a reservist who is likley to deploy, b/c they will no loger be included in the OSO's recruitment mission. As a reservist though, once in the PLC program you can drop into the IRR for no more than two yrs which makes you un-deployable. Additionally, your recruiter has no way of knowing exactly what the deployment schedual is for your local reserve unit. I doubt the CO of the unit even knows exactly.
Being an 80-90 day wonder is not a garuntee, do not count on graduating 1-2 weeks early, and it certainly doesn't me you are un-deployable.
The added benifit of enlisting is different for each person. I personally am very glad I chose to enlist, but I accepted the chance I would not get into the PLC program on my own personal timeline. You are likley to be better prepared for OCS as a prior, but as others have said, it does not mean you will be a better Marine Officer than someone with no military experiance prior to OCS.
Your surefire bet to get into PLC is to have a good PFT score, no leagal issues, and a good GPA (2.0 in min, to be competative you should get the highest possible2.7-3.2 is average for the Denver, CO OSO)