(Keep in mind that all of the "theorists" saying stacking PvP Power is always best are talking out o their !@#.)
This is assuming full buffs:
Strength always increases attack power by 2.31
PvP Power always increases damage by ~.0126%
This implies that PvP Power gets more beneficial as you get more and more attack power.
There is a breakpoint between the two stats:
The breakpoint comes out to be:
18,333 Attack Power
Until this point, Str will *ALWAYS* grant a higher DPS bonus than PvP Power.
After this point PvP Power will *SOMETIMES* grant a higher DPS bonus than Strength.
When PvP Power starts being added, the equation becomes:
where YYY represents the percentage of PvP Power already on your gear.
The numbers demonstrate that past 18,333 Attack Power (fully buffed) the best method of improving gear will be to add 3 points of PvP Power for every 1 additional point of Strength.
The easiest way to achieve this is the place PvP Power gems in Blue Slots, PvP Power gems in purple slots, STR/PvP Power gems in Red slots and STR/(Favored Secondary) in Yellow slots.
Hope this helps!