Phase 4: relatable, powerful and rewarding to win with. The fact that she looks like Kasumi and has the personality of the old Kasumi with a depressed vibe makes her all the better
Oh in that case Ayane is better, Phase 4 has better damage output but her lack of versatility, somewhat slow neutral, unsafety, and her lack of openers make her worse
Playing Ayane in DOA5LR is like playing EX Iori in KOFXIII. Phase-4 in comparison to Ayane (and her true counterpart) is a "Claw Iori" situation. A lot of tools get traded for massive damage. Ayane offers a lot more versatility as far as game play is concerned.