The idea that you can overclock a non reference card to the exact same speeds "can" sometimes be true but most often that's a bogus statement. EVGA is an instance where this is often true because the they have several non-reference cards whose only variation from reference is that it is factory overclocked.
EVGA has other non-reference cards where there are actual changes in the PCB, VRM, cooling, heatsinks, etc. MSI's Twin Frozr line has typically had a different VRM than the stock line. With the 560 TI's, the Frozr VRM had 6 phases, where as the big performers that it the record setting OC's (Asus DCII TOP for example) had 7. Then again MSI's 560 Ti Hawk and Lightning series had 8 and 10 phases on their VRM's.
Here again we have 5 + 2 design on the PE whereas the reference 660 Ti has 4 + 2. The MSI Hawk has a 8 + 2 design. All things being equal, more phases = better ability to handle higher voltages and keep those voltages stable and therefore higher overclocks.
They are the exact same price and the factory OC is guaranteed on the PE so why not ?
What I find surprising is that MSI's card is faster than many other GTX 660 Ti cards reviewed today even though it's running lower base and boost clocks. .... It seems that MSI has added some secret sauce, no other board partner has, to their card's BIOS. One indicator of this is that they raised the card's default power limit from 130 W to 175 W, which will certainly help in many situations. During normal gaming, we see no increased power consumption due to this change. The card essentially uses the same power as other cards, but is faster - leading to improved performance per Watt
The Asus DCII now also has the "secret sauce" in their BIOS but as the PE is cheaper, I have to give the MSI the edge here.
i go with pe it's a beast of a card, i plan on getting a couple of 680 lightning to compete with my dcuii tops, and of course my friends bringing over his own pe(670) to go against a 670 windforce from giga
so all i could say is based on most people's report and wacha wacha, pe is a better card price/performance you could say and should be fairly quite and not exaggerated like others where it sounds like a jet (not like they have heard one in real life where it's close enough to blast your ear drums away). but well for the answer based on my opinion I'm still not sure unless i see some personal results made.