Something I’ve always wondered: do different seals have different arena weights?

There are SP differences between sacred seals and you can pretty much follow the same logic as with the SP costs of their A/B/C counterparts.

For example: Flashing blade gives 120 more SP than spd+3 according to the arena score calc.

Seals based on skills give the same sp values as the skills.

Upgradable exclusive seals (hardy bearing, deflect ×) are based on 200 sp skills.

Non upgradeable exclusive seals (armored boots, quikened pulse ) only give 100 sp

All seals score based to their skills, for example Flashing blade scores 240sp and spd+3 120sp, then we have seals like Quickened pulse and Armored boots which are counted as 100sp