I don't think you can really compare the two (VIT and Parry) in such a manner, one gives you protection against burst damage and the other decreases the level of damage you take over an extended period of time. The math revolving around Parry rating tends to show that it's rate of gain is very small as well, when you couple that with the fact that you can only parry physical damage it makes it look even less desirable to pursue. Imo, go for the highest iLvl items available unless you're accuracy starved and/or have access to i90 crafted accessories [in the case of tanking].