Which one would be better for a growth system?

I’m making a crop growing system, and I’m wondering which one would be better gameplay wise. Doing it with random numbers or random wait times?

if math.random(1,350) == 7 then

or

wait(math.random(120,1000))

If you have them growing under a set amount of time (Ex: a Cooldown for how many times a Weapon can Fire every second, or waiting every 60 minutes to gain 1 bar of energy), then you would probably go for the wait.

math.random would probably make it more randomized, and would probably take more time depending on chance, it can grow fast, or it can grow slow.