Not always, but my impression is that it helps.
Someone's already mentioned the Gurkha's - 5foot tall and carrying a knife with a 14inch blade, 2-1/2inches across the widest part, curved like a complete bad-$%# whacker blade, and somewhere around 3/8inch thick at the spine. You only have to watch one of these guys chop potatoes for the pot with one of those kukri and then demonstrate how they kill sentries by cleaving them through the top of the head down to the bottom of the jawline with the same kukri. Skill with one's tools is what counts.
Big ? well fine, but does your reasonaing match reality ? If you said that you carried a Helle's Belle Bagwell 10" Bowie for skinning deer, I'd laugh quietly, but if you explained that it was a survival and combat tool, consistent with your belief in maximum reach and good balance, hmm, then sounds about right ...
Likewise, if you pulled out your Spyderco cricket or Mouse and told me it was your primary edged combat tool, I'd ask you to go get a Bowie. Don't care if you're 5foot or 7foot.
But to be serious, if you WERE 7foot, you should stick something like an 18inch wakazashi in your belt.
I have a self-confessed Bagwell philosophy, so there's my bias. Cheers. Jason.