Both are good choices. The Bale Taurus is clearly geared towards combat, that beast needs to be in the thick of it. Therefore you need to kit out your Sorc for combat.
The Lammasu is an interesting choice. It’s a bit more affordable and offers some great defensive boost for your Sorc. You can go into (certain) combat, but you don’t feel like you have to. And that breath weapon is serious business. I like it a lot.
A bit more on that in the Big Chaos Dwarfs Tactics Compendium