Which is better Powercolor HD7870 Vertex II with higher engine clock rate because its OC already or the new Powercolor HD 7870 Myst Edition with lower engine clock speed but higher memory clock speed and UEFI ready?
I believe the Myst Edition is better. It is based on Radeon 7950/7970 GPU (Tahiti LE) so it has more shaders and has PowerTune with Boost (975 MHz). The memory is faster as well at 1.5GHz (6GHz effective). Based on reviews, when overclocked the card reaches 1.2GHz core speed and 1.6GHz memory speed.
The Myst Edition card is basically the same Club3D Joker Card reviewed here:
http://www.techpowerup.com/reviews/Club_3D/HD_7870_jokerCard_Tahiti_LE/31.html
Review of the PowerColor Myst Edition card here:
http://www.hardwareheaven.com/reviews/1639/pg1/powercolor-pcs-hd7870-myst-edition-tahiti-le-graphics-card-review-introduction.html
Performance wise it is about the same Geforce GTX 660 Ti... not bad for a videocard costing Php 10.5K only.
You can check the benchmarks of both cards on the same test setup made by the same reviewer below. Hopefully this will help you decide.
TechPowerUp Review - PowerColor HD 7870 PCS+ Vortex II
http://www.techpowerup.com/reviews/Powercolor/HD_7870_PCS_Plus_Vortex_II/1.html
TechPowerUp Review - Club 3D HD 7870 jokerCard Tahiti LE 2 GB
http://www.techpowerup.com/reviews/Club_3D/HD_7870_jokerCard_Tahiti_LE/1.html
If I were you, just decide on which videocard will allow you to play your games at your monitor's resolution with the best FPS and graphics settings. Don't think about whether a videocard is more "pogi" or if the card is "mas matipid sa kuryente" because bottom line what's important is that the videocard allows you to play your games the way you them to be played :-)
Battlefield 3
7870 Myst - 59.2fps (12.11 driver)
7870 Vortex II - 55.3fps (12.7 driver)
Metro 2033
7870 Myst - 26.1fps (12.11 driver)
7870 Vortex II - 25.0fps (12.7 driver)
Unigine Heaven
7870 Myst - 57.2fps - (12.11 driver)
7870 Vortex II - 56.9fps (12.7 driver)
The 7870 Myst edition uses the new improved driver while the Vortex II uses the old driver. If they used the same drivers, Vortex II might get a better result. AMD is really improving their drivers. The 7870 is now better compared with the similarly priced GTX 660. Its equivalent is the 660 Ti.
I always prefer better cooling for low temps at low noise. It has a different build quality, and for the power consumption of the 7870 Myst edition, I would go for the real 7950 with lower consumption.