I'm not an dmm player and i don't have grace on our version , but i have jessica and i actually used her a lot so i tend to quite like mage armors.
I'm talking stricly by looking at the aigis wiki , so take my answer witha grain of salt



That being said , looking at stats alone , it;s obvious that grace is a defensive magic armor , while sylseth tends to be more offensive. Grace has 3460 hp and 706 defense , and with her skill she can double that (and her attack) or triple after saw , which does mean that she can probably tank golems if she has to.
Sylseth has more hp (3675) but less armor (663). She also has 50 or so more damage.


The thing with sylseth is that her skill is automatic activation and infinite duration. That in itself is really good , but she won't have the burst in damage grace will have....and even after SAW , sylseth only gets to use her 3x damage skill once before it reverts to her normal skill. Ofc , her normal skill is not bad considering she gains range and reduces magic to all enemies by 20 which can increase her and her allies damage assuming they are magic damage dealers and that the enemy has mr.


Also the fact that she has damage increase vs demons and yokai is a decent passive seeing that demons are plenty of enemies , even on our version.



I actually don't like her skill that much , untill her second awakening. Sylseth as a ultimate magic sovereign seems amazing imo. 322 range is actually insane for a magic armor , even if her skill won't do as much damage as grace. She can hit at almost double the range.




Honestly dunno what to recomand , since i haven't used any of them , and on paper both seem good. If it were me i;d rather go sylseth