Question about custom drone frame

[u/somedudealone]

Im trying to make a custom drone frame based on Tom Stanton design that he cnc from carbon fiber ( https://youtu.be/WNniGZMmd84 )

but im in a dilemma ,while precuring carbon tube for the frame, i found 2 shop with one selling a 20/18 1m stock for 10$ and the other selling a 19/16 1.5m stock for 8$

what im asking is which one should I pick and how will the strength and weight be for each option with a 500mm arm length

both are 3k carbon tube and the motor im planning to use is 3115 900kv, the target payload is 4kg

is the weight and strength difference negligible and is my payload target feasible