I'm learning Kayle 1 trick. I see most people build swift boots for AP but it doesn't feel very good for me. Is the swiftness for extra safety and slow resist before you finally hit your power spike after 2/3 items?

Personally I've been building Zerkers for AP. The 35% attack speed on top of Nashor's feel like a big difference, makes up for some attack speed from lethal tempo. The extra attack speed is better dps before my q and e become nukes after power spike, feels better when I'm behind in my lane. Helps with split push tower in side lanes too.

Fleet footwork W Exalted speed buff feels enough to make up for swiftness extra speed and slow resist.

Even with PTA, more attack speed means I benefit more after procing the third hit.

Are swift boots really the optimal boots for AP and I'm just not used to it? Or can a good argument be made for Zerkers as a good choice?