Laxus
Lightning bruiser. Tough as nails, doesn't stop for injury, one of the fastest in the series, can take unimaginable amounts of damage. Always needs a handicap to keep it an even fight. Took a blast (meant to kill him with his magical power) from Hades with no magical power and was back on his feet a few minutes later. Nearly killed Ajeel with a basic lightning attack while suffering from the magic barrier particles, according to August, it would have killed Ajeel and it scared the shit out of him, so I think Ajeel knew as well. Beat an upper tier Spriggan who was immune to his magic, tanking all of his attacks while still suffering from the effects of the MBP and had his organs disintegrated into basically a bunch of mush for an entire year. Then went on to beat Hades Histoire. Impossible amounts of magical reserves.
Gray
His most powerful opponents have all been demons, which Laxus is not. He and Lyon together couldn't defeat the Histoire of Ur. Silver? Demon. Mard Geer? Demon. Invel? Demon. END? Demon. The most powerful opponent Gray has taken out that wasn't a demon was Rufus. While not weak, Gray's not in Laxus' league. Laxus has him beat in every department. He's faster; he's stronger; he's smarter; he's more durable; he's got more endurance. Just like with August and Erza, while they'd beat others in the competition, you knocked them out in the first round by putting them with people that completely outclass them.