A shallower power supply may leave more room in your case for other things.
BUT - a smaller PSU case typically means a smaller cooling fan. That's the main difference between the EVGA SuperNova G2 and G3 models, the smaller G3 PSUs have smaller fans. While both are excellent PSUs providing extremely well regulated and "clean" output voltages, the smaller fan means it may have to spin faster to keep the PSU properly cooled. Faster spinning fans typically means more fan noise. I hate fan noise so for me, its a no brainer - make sure to buy a case that does not restrict the PSU size.
There's little point going below or higher than a 80+ Gold unit with a 10 year warranty, unless you are really cash strapped.
I agree. I tell folks not to try to cut corners in the budget with a cheap PSU. Get at least a Bronze from a reputable maker, though "Gold" would be better. Platinum and Titanium PSUs, unless you find a "too good to pass up" sale price, are just a waste in money. It would take many years of many hours per day of heavy use to make up the price difference in the energy savings the couple extra points in efficiencies the higher certified PSUs get you.
Question is, would a ABC be better than a 123 or would a XYZ be the sweet spot?
The "sweet spot" is determined by the components being supported. Not model number. Of course, buying too small a PSU is never good, and can actually be damaging to your hardware should the PSU's protection circuits fail.
But buying too big isn't necessarily a good thing either.
Most users don't know how much power their hardware actually needs and consumes. Most, even experienced uses, would be surprised to see how little it uses most of the time. This is where a nicely featured UPS or Kill-A-Watt meter can come in handy.
The right way to find the "sweet spot" and to determine the proper size needed is to research all the components, determine their
maximum power demand, add them all up, and that is the
minimum supply you should get. But that takes a lot of time and work. So I recommend using a good PSU calculator and the best and only one I use or recommend is the
eXtreme OuterVision PSU Calculator. This will calculate your minimum needs and recommend a suitable size for those needs.
Plug in all your current components. Be sure to plan ahead and include all the hardware you think you might add in 2 or 3 years (extra drives, bigger or second video card, more RAM, etc.).
I recommend setting CPU utilization to 100% and Computer Utilization Time to 16 hours per day. These settings will help compensate for component aging, and add a little extra padding to the results. This will also result in a little cooler and quieter operation.
Note that no calculator wants to recommend a PSU that is underpowered so they all pad the results, some more than others. The eXtreme OuterVision calculator is and can be the most conservative for 2 main reasons. (1) They have a team of researchers on staff constantly researching components for us to keep their extensive databases accurate and current. And (2), it is the most flexible and has the most extensive databases of available options you can enter. This allows it to factor in all possible components to accurately calculate our needs rather than guess.
The eXtreme PSU Calculator ensures you buy a properly sized PSU for your needs. One that has a little extra headroom for future upgrades, but not one that is WAY too big and a waste of your money.
Another nice feature of this calculator is it also tells you what size UPS you need.
Note that
Seasonic and other PSU makers use OutVision's eXtreme PSU calculator too (though an abbreviated version).
