Try the free version and see how you like it.
MPC1000 JJ OS
If you like it, I suggest going ahead and getting os1. You are going to have to purchase it anyways if you want the others. In other words you cannot have os2, etc., if you haven't installed and paid for the JJOS before it.
So asking which is better is kind of a mute question since you have to buy them all anyways if you really want to check them out. You can't pick one out of the bunch and roll with it unless it's the free one or OS1. Wait, there are demo versions of the next step up, but you need to have a paid version of the previous OS to audition the next.
BTW, for my needs and workflow, I do prefer OS1. The other OS versions don't appeal to me at all. However, most people do prefer os2 or 2xl, but I think it's mostly cause they do give the MPC some completely new tricks, but it's at the price of limiting some other functions, and some subtle workflow aspects that I prefer in OS1.
Plus a lot of the new functionality in os2 and xl are better done on the computer or a separate unit of some sort.