To put it simply, you will regret getting the Jr down the road.
There are a ton of things that the JR doesn't have when compared to the standard.
For starters, you only get 4 outlets instead of 8. I don't know much about your set-up, but I'd like to think you will have a return pump, lighting, skimmer, powerhead(s), heater(s) and maybe something else? Even if each device only has a single plug, you are already out of outlets on the Apex Jr. If you want to do any sort of variable stuff (dimming lights, ramping powerheads, etc), you will have to get a module with the Apex Jr. Including the module, you are now looking at $380-$400 and $450 if you want to upgrade to the 8 outlet energy bar. To me, the full apex is worth the extra $50 instead of upgrading a Jr. up to what comes with the standard on it's own.
In terms of programming and modules, etc. The Jr allows 5 while the Standard allows 240. Sure, you won't use 240 modules... but you might use more than 5.