I find Phase 4 way easier too. I also find her way more entertaining to play overall, and pulling off her flashy combos always makes me feel good about myself. XD
She's a much more basic character so yeah it makes sense she's easier considering there's a lot less to know. Those 5LR buffs REALLY helped her out as well and now everyone's picking her up
People also have a hell of a time holding her teleports. I've been using her since the day she was released and only a handful of people I've fought have been able to hold my chifu K's
I'm in the minority. I do find Phase 4 easier to use and win with, but I think Kasumi is more fun to watch. Kasumi's combos are just as flashy, but also more graceful. Also, I like that Kasumi has more options than Phase 4.