In regards to age, Kaladin is 19 start of Wok, and 20 start of OB, in Roshar years, which are ~500 days long (and longer than Cosmere standard, according to Khriss in foreword to Edgedancer)
Percy is 16 with the Mark of Achilles and 17 by the time he reaches the height of his power (by my judgement, which is House of Hades/Blood of Olympus)
Have we taken into effect the Celestial Bronze? Is Kaladin part god/monster; ie can Riptide even touch him? Probably only when he is invested. He could just stand there uninvested. Either that or is the Nahel bond enough for it to count?
And Stormlight boosts energy and heals while the Mark of Achilles drains energy. Kaladin could most likely wear Percy out and stab stab stab until he hits the small of his back. Water will heal Percy, but not forever, Stormlight however...
anyway, I’m just rambling by now