If you are referring to an "A" coil for airconditioning, bigger is not necessarily better.
If the living area was sized for a 1.5 ton air conditioner and a 2.5 ton system is installed, here is what might happen.
An oversized airconditioner (1 ton = 12,000 btu)
will not run as long as a smaller system.
This is called "short-cycling".
Air conditioning is supposed to make you feel more comfortable by reducing both the temperature AND humidity in the living space.
If an oversized system is satisfying the thermostat and not running very much, you'll end up with a cold, clammy home.
An undersized system will run continuously and do a great job of de-humidifying but an over-sized system will cool you and not de-humidify very well.
If the supervising contractor did a heat load calculation, he would know the proper size to install.
A lot of times, regardless of the calculations, a contractor will install whatever size equipment he can get a good deal on, or happens to have a lot of on hand, and the homeowner is unaware.
Nope, bigger (in this situation) is not better.