Don’t quote me since the DF ilvl scaling changes, but 20s have better tertiary stat scaling than 10s as well, ex higher speed ceiling
It was at least the case during SL
20s also get 100% speed mounts as well I think. Which will help in docks runs.
Not better, but not worse neither. Level 10 has around 85 points tert stats, with speed having 98 points (but you need 77 to cap speed).
Level 20 has around 120 tert stats, without any gems.
I finalized the tert stat scaling on both level recently, and both have around the same % if they reach the maximum of tert points (29,2% Leech at 10/28,72% Leech at 20, 39,84% Avoidance at 10/39,04% Avoidance at 20, speed cap at 49% for both, but if you don't count gems for both, you have 8 free points at level 10 and 9 free points at 20).
Level 20 have a easier time stacking speed with Shadowlands Jewelcrafting and some class has access to speed talent, that's why they have a higher speed in general