Head size explained: 98 vs 100 square inches
Head size is one of the biggest factors in how a racket feels. A larger head (around 100 sq in) gives a bigger sweet spot and more easy power, which makes it forgiving on off-centre hits.
A smaller head (around 98 sq in) trades some of that forgiveness for precision. Many improving players find they can place the ball more accurately, but they need to supply more of their own pace.
If you're unsure, demo one of each back-to-back — the difference is usually obvious within a couple of sessions.