Delta T is equivalent or nearly so across all capacities ... the airflow rate (cu ft/min) is matched to the tonnage cooling capacity.

my house is 1400sq/ft foundation. multilevel. no doors between levels. id say 2400sqft finished. i have 4 levels and only lowest level is garden level. 3 other levels are all above ground. living room is on west side. our family room is a 1/2 level down but its north side. family room is 68f now. living room is 75f. its 90f outside. we NEVER used living room. used to be off limits. its in SW side of house. gets great sun. nice in winter. but, it has always been warm in summer. maybe thats why we stayed out of it. i use family room. wifey uses living room. we have separate tv needs.

The previous system apparently exhibited the same temperature curves in the various areas of the house. Did you discuss it with the contractor regards to fixes for the problem? If not, then the new system expectedly will perform the same. Two tons (24,000 BTU) seems small for 2,400 sq ft but that depends on your location regards to climate. Equal temperature performance on all levels of a multi-level structure is difficult to achieve with a single system.

"but west side of house has no shade and indoor temp rises in afternoon"

Sounds like you first of all have a ductwork issue..... not enough air getting to the west side. And given that the condenser runs continuously in the afternoon, but fails to keep the west side cool, you may have a sizing issue also. You need to get someone in who knows what they are doing to address the air distribution and/or size the system correctly.

Size? uh, its 1 yr old. a higher cap unit means a new unit. i say put a window ac in kitchen. haha have 2 ac units running. there ur higher capacity. did i mention lower level family room is 70f. which wifey never uses now. she is parked in living room. we USED to use family room ALL the time. is storage room now. and we NEVER used living room. funny how life works.

my wifes xmas tree forest. in family room.

the cool air from living room flows down to family room. no doors.
family room is COLD in winter. great in summer.

oh, and vent to family room and basement are shut off.

this is route from family room level to living room. wish i could put in a bifold door. this is old thermo sitting on family room table.

This is path to lower level. under living room. i did put in a bifold door as we have a fireplace in basement. . traps heat well. its just too tight i think for bifold door up to living room. maybe not
I guess my point is, door traps heat in basement but will door by living room trap cool air in living room?