For the incredible bargain that is 23 points you get the same ol' Saurus Warrior stat line, and, wait for it...
ONE WHOLE EXTRA ATTACK!
Surely, you say, then they must be able to take an extra weapon, piece of gear, additional wound, better weapon skill, or higher initiative right?
**** no! They don't get anything. The only benefit you get from paying the extra 12 points to upgrade (on top of the 11 you already paid), for which you could buy another Saurus and still save a point (or give it a spear), is the ability to challenge an opponent's champion or character. That's it. Oh and if you went ahead and just bought a regular Saurus instead, you'd net +1 attack and +1 wound.
The only real benefit to buying this upgrade is the fact that you can challenge opponent's champions or characters. Except for the fact that your Champ is going last the overwhelming majority of the time. You may get lucky and the opponent might whiff, then you get to make your 3 attacks back, and hope your average of 1.5 hits (against most) can wound the jerk.
Alternatively, if your opponent accepts with most Lords or Heroes you're going to need to be scraped off his boot. Thankfully, the points you just gave to your opponent towards combat resolution probably won't matter a ton since cold blooded makes breaking combat not-so-easy.
There is some benefit to upgrading and being able to challenge, namely trying to get Teclis or some other Wizard to decline the challenge, tie up a character for a turn or so, or get a nice string of luck and kill their Champion/Hero/Lord. Or to protect an Old Blood or Scar Vet (if you have one).
However, since challenges can be issued by either player in any close combat, regardless of whose turn it is, odds are pretty good that you'll end up losing a champion and possibly some overkill wounds to combat resolution. The nice thing about not having a champion? You don't have anyone for an intelligent opponent to challenge, and you gain 12 points per Saurus block that otherwise would have taken one.
However, since challenges can be issued by either player in any close combat, regardless of whose turn it is, odds are pretty good that you'll end up losing a champion and possibly some overkill wounds to combat resolution. The nice thing about not having a champion? You don't have anyone for an intelligent opponent to challenge, and you gain 12 points per Saurus block that otherwise would have taken one.
I run 3 blocks of Saurus in a 2000 point army, so I end up gaining 36 points that can be spent adding Chameleons, upgrading my TG's magic banner, etc.
*Of course, if you're running a Light Slann, Saurus champions issuing challenges are much more effective. Speed of Light and/or Birona's Timewarp can make issuing challenges offensively pay off. With both, your champ is WS10, Initiative 10, ASF (rerolling missed hits), and 4 attacks. Very potent indeed.