Item ID is definitely better from a damage perspective, you are doubling the vanq effect of 25% at 100 Item ID, for a cool 50%, or 55% with 120 - the increase isn't huge, and if only using vanqs, forensics maybe more beneficial with colored leathers. If the item also has slayer effects it increases those as well by 60% at 120 skill - make them much better.
Vanqs were always the go to over avarite because backstabbing gives an accuracy bonus, and vanq was always higher than avarite in terms of damage bonus.
Forensics at 120 is 30% damage bonus - so the 19% + 30% is still only 49%.
The real question in all of this - do you have access to vanqs (and is it worth it for a slight damage increase), and if you do have vanqs with slayer properties, are you going to risk them considering the value they could have?