Just seasoned a Dutch oven with tallow for the first time and would recommend that if possible. Avocado has been my go to in the past.
Since you've used both, could you articulate the differences between avacado and tallow?
The difference was mostly in origin. I render my own tallow so I know what it is and where it comes from. Avocado oil has a higher smoke point than what temp I season my pans at, usually about 450F which is pretty close to tallows smoke point. Don't know if any of that matters really I just like using my tallow and it's easy to handle.