Hi Paolo,
in certain configurations, the XMG NEO Series has a slightly larger power supply in order to accomodate for the "OverBoost" feature, which increases the GPU Performance to levels that are slightly beyond the norm.
Other than that, I wouldn't mind the power supply so much. All of these series have more than enough power. These decisions are usually made very early in the product plan process because they are part of the certification.
In other areas, the differences between XMG PRO and XMG NEO have been explained thoroughly. XMG PRO shines with lots of ports, storage, features, polish, bells and whistles, while the XMG NEO is a bit edgier with M/E keyboard and cutting edge Overboost feature. Both are very fair choices and it comes down to personal preference in the design and feature area.
Cheers,
XMG|Tom