Hi, Michael. A great place to ask that would be in our user forum here: http://forums.camerabits.com/index.php#c2
There are quite a few people who have been part of our open beta program and have been using Photo Mechanic Plus beta for a while now, and they'd be able to give you their pros and cons. The biggest benefit of Photo Mechanic Plus is that it lets you quickly search and find all your photos - even on media that is not currently connected to your computer. Not everyone is going to need that in their workflow, and that's fine. If you'd like to try it out and see, we do offer a free trial.