Hello Sam,
I have been thingking a LOT about the best Poser default figure and the way to model it.

I came to this conclusion : Model in the standard "T" Pose.

Why?
Clothing making, Props making, Industry standard, are the major reasons.
YES. you will get texture stretching on the collars-shoulders when you lower the arms. But a good texture maker can overcome those.

The only thing I will not model in a "T" Pose are the breasts.

I model the breasts in a "arms-down" pose.
When a woman lowers her arms, the breasts drop 1 to 2".

99% of the poses are arm down poses. So 99% of the time they (and the texture for them) are flawless.

Modeling that way gives the least problems and is the most "end user friendly" way.

Poser 1, 2, 3, 4, 5, 7, P8 and PPro2010, P9 and PP2012, P10 and PP2014 Game Dev
"Do not drive faster then your angel can fly"!