What is the typical space allocated to first class vs. economy class passengers?
Width and pitch give you the space that is allocated to you and your seat. First Class seats are more bulky than Economy seats, so the actually usable space is a smaller fraction than in Economy. I wonder how the square meters would convey more information; generally, in Economy you are boxed in by your neighbors, while in First you can outstretch without reaching the limits of the cabin space allocated to you.

The aisles are wider in First, but it will be hard to make a concrete claim on "your" part of the aisle. Cabin crew in First will be more tolerant of eccentric behavior, so your mileage varies. Also note that in First on wide-bodied Aircraft every seat will have direct access to the aisle, so you will not need to step over the feet of your neighbor.

You also get more space for your baggage (luggage). On narrow-bodied aircraft two people sit in First Class where six would sit in Economy, so you get three times more space in the overhead bins. On wide-bodied aircraft this difference is even more pronounced, count on having in First the space of 5 ore more Economy seats. The bins are smaller, though.

Also, the steward will take care of your coat in First, so your space requirement is reduced as compared to Economy.