I don't know if I would say stronger, but Obi Wan did change his fighting style because of Qui-Gons' death. Obi-Wan favored Form IV just like Qui-Gin. But he saw how flawed it was in tight spaces. That's how Darth Maul got the edge on Qui Gon.Obi Wan changed his lightsaber form to Form III after that.I do think training Anakin and fighting alongside dud have some impact, though. I remember in the ROTS novelization that Obi Wan learned to relax and not be so uptight due to being around Anakin