The KF V4 is not a simple Orchid or KFL. Even a 12$ KFL can be waisted money and there are lots of crappy KFLs around.
If the cheaper V4 would be from Ivogo, I would choose the Robbot.
If a Hotcig V4 version would be 30% cheaper than the Robbot, I would take the Robbot.
If a Infinite version would be available for the same price, I would have to ask a dice.
I would buy only V4 versions from Infinite, Robbot, Limwell and EhPro.
Btw: even the original V4 has not a perfect spring. If you use a mech. mod and a coil below 0.8 Ohm, you can have a voltage drop of 0.3 Volt ( 0.05 Ohm). But when you stretch the spring you can lower the voltage drop to less than 0.1 Volt.
If the cheaper V4 would be from Ivogo, I would choose the Robbot.
If a Hotcig V4 version would be 30% cheaper than the Robbot, I would take the Robbot.
If a Infinite version would be available for the same price, I would have to ask a dice.
I would buy only V4 versions from Infinite, Robbot, Limwell and EhPro.
Btw: even the original V4 has not a perfect spring. If you use a mech. mod and a coil below 0.8 Ohm, you can have a voltage drop of 0.3 Volt ( 0.05 Ohm). But when you stretch the spring you can lower the voltage drop to less than 0.1 Volt.