Item level does give you a great deal of information, however you are looking at trinkets. Trinkets because of how they function must always be looked at independently because you won't always find an identical trinket stat/effect on all tiers of content. Actual gear such as a helm however you would typically find the higher item level to be better almost all of the time because of the higher primary stat values. Going from say a parry/mastery item to a dodge/mastery item from one tier to the next makes relatively little difference since secondary ratings are rebalanced through reforging. You should always be aware of relative stat values because it is always possible that an item high in a secondary stat you favor being traded for an item completely missing it may be significant enough of a loss to overtake the gain in primary stats on the higher item level, most of the time however this is not the case.
Trinkets are always the exception to the general rules because their effects vary from item to item.
"In anything, if you want to go from just a beginner to a pro, you need a montage." /w TankSpot WTB Montage for Raiders.