I checked out Heathrow's new Terminal 5 yesterday.
Like Pearson, it has plenty of natural light, a neutral grey/white colour palette, minimal signage and clutter, and large structural supports that double as decorative elements.
Pearson's top floor "big wow" is a long, snake-like check-in building with windows at both ends ... that you exit in order to reach the departure lounges and retail.
The top floor "big wow" at Heathrow is a larger rectangular departure level with windows at both ends ... that's split lengthwise by the check-ins and has to accommodate more functions, including retail. The arched span of the ceiling is wider that Pearson's undulating ceiling. But half of Heathrow's departure level is beyond the check-in area, so you can't explore the whole room - I felt a certain frustration with this design approach and the "big wow" was diminished.
Public art, which is an integral part of our new terminal, wasn't much in evidence at Heathrow. But the vertical connections between floors were handled better. Nice concrete ceilings ( like our Museum station ) in the subway station below.