Can somebody explain this ?

Greetings Im Noexit.
A few days ago i found out a weird way of calculating healing (for priest at least , havent tested this on any other classes ). The tests that i have conducted consists of swaping full pvp gear and full pve gear to find out whats the difference in healing done ( The healing delt on the pics is from Renew the difference is the same with the other healing spells as well). The result were confusing. Battle Fatigue is not present in the test.
PvE gear healing test - http://prntscr.com/9fuk7x
As you can see on this 1st screenshot im wearing full t15 set (No parts of the gear have intelect gems in them only haste and spirit gems ) with also some 530 ilvl pve items ( i have removed the weapon and cloak to remove the RNG procs from Jade Spirit and Tailoring Empowerement ).The amount of spell power that im sitting at is 19639. The healing done by a tick of renew is 16295.
PvP gear healaing test - http://prntscr.com/9furnk
For the second test im wearing 4/5 Griev set pieces and Griev off set pieces( I havent changed the trinkets in order to keep the intelect gained from them a constant ). The amount of spell power that im sitting at is 18304 . The healing done by a tick of renew is 17770.
Also take in consideration that the Griev items that i have equipped have NOT enchants or gems in them , making the difference in healing even greater.
Could somebody care to explain why is there a difference of (17770 ÷ 16295 = 1.09) , 9% more healing in favour of the pvp set when i have more spell power and higher ilvl items equipped ? Does this mean that you can go to raids fulling griev geared (just have pve trinkets) and outperform the other full pve geared players ? Whats the point of pve gear then ?

There is a chance that the PvP power stat is outperforming the spell power one, somehow... GeoGebra and Volfram Alpha would know well, because it increases the healing power Outdoors... Go in ToT or MSP, and try there :)

Have you ever heard about "PvP Power"?
PvP Gears gives "PvP Powers" which increases damage by "x" and healing by "y". It works outdoors and PvP Areas.
As Cheinii said you need to enter in a Dungeon to make proper test because in Dungeons/Raids "PvP Power" does not work

It is a formula :) Take it from Wowhead, put it in Geogebra or Volfram Alpha, and find out if it is better to have more Spell Power, or PvP power... but if i recall correctly, this works Only for healing, and not damage! Thus, just take the Turnip and check the damages as well :)