Hello.

Say for a model of a character, whats the advantage in having everything on one texture, as opposed to have everythiing through several (3-5) textures?
Will there really be a difference in power/memory...well, of course memory, but power?

Whats the advantage or disadvantage?

in game design it is always necessary to do things with using almost no performance.
so yeah, if the game has to load 3-5 textures for a single model it uses more power than using just one single texture. (depends on the texture size though... four 128*128 equals one 256*256)

my models always just have one texture, except when im shading... then i'm adding specular, lightmaps, etc...

if you want to tile your images on the model [defining materials like in the 3d raytracer apps], i'd recommend some smaller maps. example: you modelled a car, so the color map can be extremely small (map1), you'll need something for the windows (map2 with alpha), and a leather map/wooden map for the interior (3 and 4) plus, it's easier to access single maps with shaders than masking with alpha, so map1 gets a specular shader, 2 an alpha material, 3 and 4 a bumpspec shader.