the 320 is more efficient but also it is self switching on the input side, ie no need to change a switch for 110 or 230vac.
that is pretty much what I can see as the main difference. Unless you are travelling the world with your display, I don't see a need to pay the extra for it
As the purchaser, you will need to determine if the better specs are worth the cost difference.
The Meanwell RSP series specifications are pretty much all equal or better than the LRS series. I would add that the PF correction and better efficiency will lower its operating cost although I'm not sure how much. David_AVD sums it rather well, in just about every instance, a cheaper product has a lesser quality. Mark_M mentioned certifications, although I think Mark meant the RSP has better certs than the LRS series. Meanwell's market point is directed at a tighter spec use; RF and test/measurement instrumentation for the RSP series.
Too, if there is a particular supply specification you do not understand or are curious about, those of us here will help best as we can.
The supply pictured in your inserted graphic is a single output supply. All of the +V terminals are connected together by traces on the PC board. So too are all the -V terminals. As mentioned by 'uncledan', you can use any one, any two, or all three of the +V terminals. And again, so too for the -V terminals.
It is fairly common for higher wattage supplies to have multiple terminals to spread current draw. This helps prevent heat damage to the PC board at the terminal/PCB junction. It also allows smaller diameter wire to be used if the user prefers in which case correct fusing needs to be considered.
Yes, a single power supply can feed multiple controllers, or more than one side of a single controller. Just make sure that the wiring is heavy enough and that the power supply is rated for the total load (of pixels) you're powering.