Hello, I know that stats are scaling different between levels, so 10 haste on level 30, is buffing far more haste % than 10 haste on level 120.
So hope this makes sense and is not to complicated to understand.
But as far as I know, each stat on each equipment will scale the same, depending on your character level.
So if you need 100 extra in your main stat, then a Flask or Potion with a +100 main stat buff, is the same as finding an equipment that gives +100 in a main stat.
But also, if you take a Weapon with +100 Main stat, and a Trinket or Ring with +100 Main Stat, is all the same with scaling.
Meaning that +100 main stat on a weapon or equipment will give same boost to spell or attack damage as a main stat on a ring or armor.
And a if you need the +100 stat, even if it will be limited in time of course then +100 stat will always scale the same regardless of the source, and regardless of item level also, only decided of character level.