YZZF1 has a different filter element arrangement than the YZZA1, the former being more "traditionally pleated". For "cost cutting reasons."
This maybe a bit off topic, but I remember someone said that all Toyota 4-bangers use the same filter. I changed to YZZF1 from a YZZA2 in my 97 Camry LE 4Cyl already. Fits perfectly. My 99 Corolla also uses YZZA2 so I'm going get another YZZF1 for it, so I can go at least 8k between oil changes on Mobil 1. They are the same price yet YZZF1 is taller. Go figure.