I have the PSL4. I consider it to be the single biggest purchase mistake I've made for my pool. Not the Pentair part. Not the 4 part. It's the Lite part! I have a simple pool, no spa. I have a light. And solar. And a couple actuators (solar and cleaner). It can run all that just fine. But it's the scheduling that is so severely limited in the Lite model that I can't do what I wish I could. And the whole point of paying for automation is so you can schedule things!!
I could easily use 8 different schedules, but can only have four. The ET has a nice feature, called Egg Timers. So say I want to have a setup where I push a button and my pool gets an extra fast skimmer session, just a manual thing, outside of the normal scheduling. Great for guests coming over to a "leafy" pool, right? The Egg Timer would shut off the fast skimming after some predetermined interval, say 30 minutes, so that I wouldn't have to remember to turn if off (like, right when guests are arriving and I'm pouring). But the ET counts an Egg Timer as a schedule. So to use the Egg Timer feature, I'd have to get rid of one of my regular schedules!! Etc. That's just one example of its limitations. I could list a half dozen others. Don't get the Lite, you'll be sorry you did.
Regarding the Load Center, that's #2 on my hit list for the Lite. Without one, I have to have a separate set of breakers in a nasty looking grey box, with thick conduits running between it and the ET. And another big separate clunky box that houses my SWGs transformer. Pool pads are ugly by nature, so maybe that would mean nothing to a normal person, but I'm OCD and wish the ET I had purchase had the transformer and circuit breakers all built into it's attractive box (there is such a model, that comes bundled with an SWG, that gives you a little price break). It bugs me every time I walk by my pad!!
That aside, I like Pentair, the ET has functioned well for me otherwise and I have all its remotes and such that allow me to control the pool from my phone, iPad and any of my computers. Very nice. Even while away from home. I splurged and have yet another controller mounted near my thermostat, so I don't even have to find my phone and wait for an app to load. I can just punch a button while walking by it. Jim's not a fan of that add-on, because it is pretty old school, but I use it multiple times a day, every day. More than the apps.
Hope that all didn't confuse you more than it helped! Whatever model you're considering, I can whole-heartedly recommend automation in general.