variables.

The  payload: lift-off WT ratio depends on:

1)As I said specific impulse which represent engine/fuel type efficiency; like one measures a truck's efficiency by diesel used for 1 ton(vehicle+load) over 1 km

2)No. of stages. A 3 stage one has higher payload than a 1single stage one of the same take-off mass,tech level&fuel.

3)Thrust to WT ratio at take off; your favourite.

4)Size of rocket. a)A 1000 ton rocket might only need the control system of a 500 ton one. b)Air resistence proportional to square of dimension and mass proportional to cube of dimension, ie, bigger rocket has less air resistence per ton of mass. Size matters and has its advantage

5)Latitude of launch site: Equatorial site has advantage over higher latitude sites when it ccome to launching load with low inclination with equator and also GST load. Like the french Guiana site has natural advantage over russ sites. It has to do with higher tangential speed due to earth rotation imparted on the rocket.

6)Higher fuel fraction or lower structural weight. Here the Falcon 9 has an advantage I can't explain. Its fuel fraction(as% of stage or booster weight) is something like 95% compare to 90% of Delta IV or LongMarch 5. It means the Falcon 9 can 'save' a few% of weight for payload. I'm not sure if they made some advances in material tech or they don't care about the risk. One can wait and see. That seems to be the main reason why Falcon 9 has about the same payload:lift-off WT ratio as Delta IV even though the latter has higher specific impulse

Falcon:  https://en.wikipedia.org/wiki/Falcon_Heavy

                                         1st stage                                       2nd stage

Delta IV: https://en.wikipedia.org/wiki/Delta_IV_Heavy

CZ-5 :   https://en.wikipedia.org/wiki/Long_March_5

Boosters

core stage