I think the "Professional" models are the kind you'd find on route and the "Home" models are scaled down a bit and don't have coin slots. Anyone know for sure?
The only one I have had any experience with was Batman: The Dark Knight, so this info could be flawed but I think this is how Stern does these:
Home - one non-functional coin slot, game is set to freeplay in the software and can not be changed. Some dumbing down of the rules / removal of "expensive" game pieces. Think of it as a stripped down model that collectors really don't want.
Professional - this is the machine you will normally see on route at your local bar or arcade. I believe the majority of the pins from each theme will be Professional models.
LE - This is the limited edition, geared towards the collector crowd. Upgrades are primarily cosmetic and the software may be more advanced. These normally come out a little later and are fully ready to go on route if you desire.
One thing to consider when buying a new Stern pin - they have a very Microsoft esque attitude towards software. Early software releases are usually buggy and incomplete. This is completely fine for the casual bar player but home owners and really good players playing a game on route often bitch about the machines until the updates fix all of the problems. If a machine doesn't sell well Stern doesn't put much effort into updating the software, so you may end up SOL with a partially working machine.
Updates are easy to install, just download the file from the Stern website on a jump (thumb) drive and plug it into the machine. As far as I know updates are always free.