There are too many different LEDs on those lists. Here is a 3mm bargain pack of 100 LEDs from TX how is a person suppose to know what they are? So if they are same voltage & current as 5mm they are just as bright. Looks like I need a 2D batteries and a resistor.
It depends.Does 5mm LED make more light than 3mm LED ?
The 18 LED security lights that I built wires rusted out in the weather with no protection it is easier to start over build new LED flashers with LDR on the same PC board. I ordered new LEDs but did not notice they are 3mm until they came in the mail. Cross sectional area of 3mm is 64% smaller than 5mm that alone makes them harder to see in the dark. I think I will build a circuit with 3mm LED just to see if I can see it in the dark 200 ft away.It depends.
I have found most 3mm LEDs have max 10 to 20mA current rating and 5mm typically have 25 to 30mA rating. The voltage is a function of the band-gap (chemistry and doping) and therefore independent of diameter.
Other people may have dealt with different 3 and 5mm LEDs so they will have different answers. There are about 3000 3 and 5mm LEDs at my distributor. I'll let you look them up.
Now that I've written all of that, are you willing to tell us why you want to know?