Regarding nVidia's boards, the GF1 did have power issues but the MX/GF2/Ultra don't because they are based on the .18 micron manufacturing process.
As for the Voodoo 4, I remember reading something in one of the V4 reviews that said 3dfx are still using the .25 micron process for the V4/V5 while nVidia are using the .18 micron process. If that is true then the V4 will definitely draw more power than the GF2 MX.
As a side note, if you read the 3dfx FAQ for the Voodoo3 it would seem that they also had power issues with certain AGP motherboards.