August and Irene are obviously the strongest. Other than that, I see most of the other Spriggans being on the same level in terms of magical power, with only their abilities dictating what situations they would be suited for in combat. I honestly have no idea where this idea of Ajeel being a fodder among Spriggans came up. He was stated to be on the same level as Brandish. Or this idea that Jacob would not be a Spriggan-level mage if he didn't have his transport. He would still have his magical power even if he couldn't cast one of his spells.
In terms of direct combat, God Serena and Wahl are probably the strongest. To this date, God Serena is the only Spriggan with victories under his belt and his opponents were the Ishgar Saints + Jura. Jura alone is impressive enough to have been hyped to be a match for Gildarts, and gave GMG Laxus an incredibly difficult match. Serena stomped not only Jura and 3 even stronger opponents in his base form. Wahl has the ability to cast etherion, and that probably means he has the strongest attacks out of any of the Spriggans bar Irene/August. Regardless of whether or not it rivals the council's etherion, that's still impressive. A chunk of etherion was enough to give Natsu enough power to enter dragon force, and beat Jellal. If Wahl can produce a decent sized beam, he would have a massively powerful attack.
In terms of durability, my view on this is simple. All the spriggans who do not have magic that modify or enhance their physical bodies have similar durability, unless feats dictate otherwise. Ajeel, Brandish, Jacob, and Neinhart would all have similar durabilities. God Serena would have enhanced durability when activating his dragon slaying magic due to the magic giving him qualities of a dragon's - and then further resistance if its one of his 8 elemental attacks. Dimaria would have enhanced durability under God Soul, which I assume would be no lower than something like the God of War's.
In terms of utility, Dimaria has the best hax against an unsuspecting opponent, which allows her to negate the need for direct combat. This lets her potentially beat the other Spriggans. However, Age Seal does not make her attacks stronger, nor does it negate someone's passive durability. She can't take out anybody that can tank the entirety of her arsenal of attacks, whether or not she has age seal. There's a tendency to go overboard with Dimaria's capabilities, but I think it's safe to say that since Zeref also possesses the means to stop time and August knows every type of magic (probably including time) that Dimaria can't beat anyone Zeref or August can't. Bradman's anti-magic particle body would allow him survive Dimaria's attacks. Interestingly enough, Bradman's anti-magic particles can be countered by Wahl's ability to cancel them. Jacob also has an effective ability for avoiding direct combat, but he needs to clap to perform transport - meaning it's probably slower than Dimaria's ability to cast it.
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