Is the scar-vet a better choice than the Oldblood for the carnosaur build?
I saw that they share the leg and half the body so magneting them seems to be impossible..
Well the Scar veteran works better when it comes to buffing your allies, plus he has a shield that negates -1 rend.
For instance, say I wanted to make a build like this:
Warrior Heart
Scar Veteran on Carnosaur: 260 (General, Relic blade item on spear, Charge or Defender command trait)
Loremaster: 100
Celestial Hurricanum: 320 (phoenix stone item)
Starseer: 160
Skink Priest: 100
Unit of 15 Chameleon Skinks: 360
Sunclaw Starhost: 80
Sunblood: 120
Unit of 40 Warriors: 400
Unit of 10 Warriors: 100
Unit of 10 Warriors: 100
Total point cost: 1980
Your Scar Veteran could buff your 40 Warrior stack with his command. His command lets you gain another attack on a hit roll of 6 or more. Now, the 40 Warrior stack gains a +1 to hit when they have 20+ models, and an extra attack if they have 30+ models with their spear, as well as an extra bite attack thanks to the Sunclaw Starhost. Also, if you put your Celestial Hurricanum near them (which has a auro buff that gives +1 to hit to order units) they will get a total of 2+ to hit. Which means that on a hit dice roll of 4 to 6 you will gain an automatic free extra attack!
Combine that with the Loremaster's hand of glory, and you will have a lot of chance to get these extra attacks. Also, if you give your Warriors spears, you can first attack with their bite attacks, and then if the opponent moves away the front enemy units to try and deny your main weapon's attack, you can more easily pile in again.
Also, if you place your stack of 40 Warriors just 2" behind your 2x 10 Warrior stacks, I believe you can attack from behind your 2x 10 Warrior stacks as long as you spread them out a little. This means that those 2 stacks will soak up the damage, keeping your main stack as healthy as possible.
And if you place your Curse of fates from your Starseer on your Skink Priest, you have a higher chance to activating his protective aura buff. Should you still fail, you can (hopefully) use one of the Starseer's rerolls to correct that. The Skink Priest gives a 8" aura, and as long as one model of a unit is within that aura, you can rerolls failed charge, run, and even save rolls.
Put a Mythic shield from your Celestial Hurricanum on one of the 2x 10 Warrior stacks, and you have a decently strong front defensive line.
Simply put: The Oldblood on Carnosaur is stronger as a single model, but the Scar Veteran on Carnosaur is stronger when it comes to buffing a powerfull Saurus unit, such as a 40 Warriors stack.