You can hit Sephiroth about 20 times before he teleports in 2. In 1, he teleported after you hit him the fourth time. While he may have been an easier opponent in 2, Sora had a lot of invincibility frames in 1 with his techniques such as Sonic Blade, Ars Arcanum, Strike Raid and Ragnarok which made the fight overall about as difficult as the one in 2. That's just the way I see it though.