the advantage i see to different length tree straps is you don't have to wrap around a small tree a bunch of times to take up a bunch of slack. i like to have as little webbing extending from the tree as possible since it stretches more than the line will.
i have thought about sewing an intermediate loop maybe half way on the strap, this way, it would work as a short or long strap depending on what you needed.
that 7/64 is what i was talking about, they are both made from samson if i'm remembering correctly. i thought they were both 2.75mm i can't remember. the amsteel blue is just a stronger dyneema i think.