Triforce vs Infinity Edge

Triforce always adds 150 damage

18 pirate has 100 base attack & 12% crit chance
Base Parley = 260(520 crits) = 291 avg
Parley + Triforce = 282+150 = 432(714 crits) = 499 avg 24% crit chance
Parley + Infinity = 348(870 crits) = 515 avg 32% crit chance

So not only does Infinity adds higher burst then triforce, it also bursts more often and it also adds more damage over time, also you would need to get a bit of magic pen which you dont need anymore for triforce, infinity edge uses your armor pen instead

Infinity Spam - http://www.leaguecraft.com/builder/G...47cb3e6decab57 100% crit
150+611 = 2209crits, average armor is 70, on a 2k hp you do 64% of his hp
150+611 = 2209crits, tank armor is 200, on a 2k hp you do 36% of his hp

GG v2 - http://www.leaguecraft.com/builder/G...47cb3e6decab57 91% crit
150 + 545 = 2015crits, lowers enemy armor to 48, on a 2k hp you do 68% of his hp
150 + 545 = 2015crits, lowers tank armor to 120, on a 2k hp you do 45% of his hp

but first one will probably do less but it will always crit, while 2nd one only has a 91% crit chance

Triforce adds other stats such as slow, although I prefer IE.