Having done both (my AD decided to make an 'arms down' model for our last game), I have had many more deformation problems with a T pose than the other extreme. Weighting with the arms down was a real bitch (especially since it was an anthropomorphic dragon character and practically self-intersecting), but the deformation…
I'm not sure what your goal is for creating art. Is it just a hobby? Something you want to do for fun and your own personal satisfaction? Or is it something you wish to go into as a career choice in the future, etc.? If you are looking at it as a career thing, I would strongly suggest finding an engine that supports…