Yes, i get this question asked a lot through the forums and in-game, so i have found this useful information that work out the maths behind each one
Note: the increased stats drain wasn't taken into affect as it acts differently depending on who you're fighting.
Note 2: all % in here are multiplicative. For example a 5% increase in accuracy would change a 55% hit chance to a 57.75% hit chance.
Note 3: The following gear was in all the setups Tectonic, Amulet of Souls, Ring of Death, Virtus Boots, Celestial Handwraps and an Illuminated God Book. There was slight rounding here.
At the bottom I'll show the formulas and an example but here is the data.
T90 + Turmoil = 2267.1 damage, 4687.7 accuracy
T90 + New Prayer = 2316.7 damage, 4775.6 accuracy
T92 + Turmoil = 2298.8 damage, 4807.1 accuracy
T92 + New Prayer = 2348.9 damage, 4894 accuracy
Here's how the upgrades work
Using t90, buying new prayer = 2.19% Damage and 1.87% accuracy = 4.06% increase
Using t92, buying new prayer = 2.18% damage and 1.83% accuracy = 4.01% increase
Upgrading t90 -> t92 = 1.40% damage and 2.55% accuracy = 3.94% increase
Upgrading BOTH = 3.61% damage and 4.42% accuracy = 8.03% increase
Based on this I would upgrade with the new prayers first before upgrading to t92, with the exception of a SOS for telos.
Sample
Damage
T92 weapon, 128 stats (turmoil) and 190 style bonus
Ability Damage = 3.75×128 + 14.4×92 + 1.5×190 = 2089.8
That then gets multiplied by 1.1 due to turmoil = 2298.78
Accuracy
F(128)+ 2.5×F(92) = 2229.7 + 1030.9 × 2.5 = 4807.1
Credit's to RsHeemo