>1. PFC is not the same as efficiency. There could be two
>PSUs with 65% efficiency, but one with 75% PFC and
>another with 99% PFC.
Right. Here 'efficiency' refers to the AC-DC conversion efficiency of the power supply. A 65% efficiency would mean that 65% of input power is converted to output power and the rest is generated as heat (and perhaps some noise / magnetic emissions).
>2. Active PFC PSU run more efficiently in drawing power
>from the Hydro company. So, the better the PFC, the less
>the power consumption resulting in smaller hydro bill. (not
>too sure about this since this kinda contradicts the first
>point)
Right. PFC avoids harmonic distortion load on the electricity transmission lines which results in reducedheat generation in transmission equipment, reduced likelyhood of broken transmission equipment and increased overall power transimission efficiency.
It's good for the utility company and at least in some parts of the world the utility companies charge you for the power you use AND the harmonics you produce. Hence, better the PFC the less one pays to one's utility company.
In EU the demands for a PFC supply of 300W or more power are such that practically all ATX PC PSUs sold here should be Active PFC. However, that doesn't seem to be the case yet. This puzzles me, but so do many other things regarding EU
>3. Active PFC's are more efficient, so they run cooler and
>are easier to cool down.
This is true when compared to a particular passive PFC design. I'm not 100% sure about this when compared to a non-PFC design. I'm now talking only about the efficiency of the PSU, not the efficiency of the electricity transmission down the lines.
My layman thinking would guess that a APFC PSU would probably be slightly less efficient (as a PSU) than a NON-PFC PSU, due to the APFC circuit power needs.
However, this is probably more of an implementation issue as one can make a really bad active PFC PSU and a good passive PFC PSU. It's mostly in the design.
Perhaps somebody who has more understanding about PSU design could chime in?
>4. PFC got nothing to do with more or less power.
>Meaning that two identically rates PSU with and without
>actice PFC would deliver the same power.
In theory yes, in practise it may depend on some factors. If the designs were identical sans the APFC circuitry, then probably for all practical purposes the answer would yes (I'm not totally sure, I'm not an expert on this).
However, as the PFC circuitry may change how the PSU operates in under-voltage conditions, the performance might not perhaps be the same on a really bad line (i.e. problems with the utility company). Again, guessing here.
>5. Efficiency: non-PFC < Passive PFC < Active PFC
For PSU efficiency, I'd guess that the theoretical (best of design) order would be:
non-PFC > active pfc > passive pfc
However, I believe the PSU efficiency is probably more the function of it's design and implementation rather than whether it's a PFC unit or not.
For transmission efficiency the chart is more than likely as you describe above.
>6. Active PFC is preferrable PSU.
Over a passive PFC PSU (higher PSU efficiency, less heat, less likelihood for additional conversion noises, better use of transmission power): Yes
Over a non-PFC one (higher transmission efficiency for your utility company, perhaps smaller bills for you, good for the environment): Yes
That's my take on things, but there are special situations where a passive PFC or a non-pfc unit might be better.
For a general home PC use I'd recommend A PFC as the best solution though if all other variables remain almost constant (i.e. heat/noise/price/etc).
regards,
Halcyon
. Also, some said to buy a passive PFC since it's easier to cool with low flow fans. So, either I am missing something here or those posts were not accurate. 
His last point -- APFC is best -- is right, AFAIK. Just a few confirmations & observations: