Fallacies of Ambiguity

This afternoon I was talking to my friend eugene. I asked him i prefer portrait / shooting fashion shows so the question is what lens should I get? But I told him I wanted a fix appature lens that is F2.8 lens or more knowned for nikkor lenses are those lens that has a gold ring at the front of the lens. This range of lens are at the top of the range the cost a bomb to own them easily cost over RM4000. 

So in the end herecomended 2 lenses. 

1. Nikkor 70mm-200mm F2.8 VR this is a telehpoto zoom lens.

2. Nikkor 85mm F1.4  Portrait lens, very very sharp but fix focal length 

So the debate was going on for 1 hour and he told me this 1 is good for this tat 1 is good for that so which one u advise to buy??

Eugene is using one of the fallacy that I learned in BCT1024 (critical thinking). The Fallacies Of Ambiguity is applied here. Because Eugene made me very confused in deciding which lens to buy argH!