LogFAQs > #905125245

So, one of the key things to look for in CEs is the stats they give. Some of them are 100% attack/0% HP, some 60/40, some 0/100. For your offensive Servants, you want the CE to have as much Attack as possible, since offense is way more important than defense in FGO (it's one of the reasons that you don't want to use a 2030 on your attacker - it's incredibly useful, but it only gives HP. It's also the reason Bond CEs are bad - they only give 100 attack and 100 HP). At level 100, Golden Sumo gives a bonus of 2000 Attack, which means your Servant with not so great stats is suddenly a monster on par with much higher rarity Servants. This is awesome on everyone, of course, but it makes an even bigger difference on weaker Servants - going from 9000 to 11000 ATK is much bigger than going from 14000 to 16000 (though the latter is still awesome).

The 15% ATK boost is 15% no matter what, yeah.
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