Create a skeletal champion magus using create undead
To put this in perspective, I'm using the third printing of the Bestiary (originally published 2009) that on Variant Skeletons says
Perhaps the most dangerous variant skeleton, though, is the skeletal champion. This skeleton retains its intellect, and often any class levels it possessed in life. A skeletal champion cannot be created with animate dead—these potent undead only arise under rare conditions similar to those that cause the manifestation of ghosts or via rare and highly evil rituals. (251 and emphasis mine)
Then Classic Horrors Revisited (2010) introduces the skeletal champion variant magus (55) that's mentioned on d20PFSRD in this entry for Skeleton. (Ultimate Magic (2011) would describe the entirely different character class magus.) Thus, while skeletal champions could now fight and cast spells, there were still no instructions for their creation.
Finally, although the text itself isn't mentioned on d20PFSRD, Undead Revisited (2011) makes it relatively clear (on a table on page 3) that a skeletal champion can be created using the spell create undead just like the d20PFSRD describes. (This reader assumes that this includes variant skeletal champions like the skeletal champion magus, but, as always, ask the GM.)
Anyway, no matter what, the spell animate dead can't create a skeletal champion or any of its variants.
A skeletal champion magus will usually be a better investment than a normal skeletal champion of the same level or lower (and often higher!)
A skeletal champion magus is pretty much in multiple ways a power-up compared to a normal skeletal champion. I mean, of course, the skeletal champion magus gains a bonus feat, but—more importantly—, a skeletal champion magus can cast magic spells, therefore employing the game's most powerful force. Still, the typical problem with creating a bunch of skeletal champion magi is that finding the corpses of dead spell casters is usually much more difficult than finding the corpses of the mundane warriors killed by the spell casters.