Probably a very personal choice although I wonder how much one is influenced by the coil that any tank comes fitted with. So far, I have stuck with each coil that each tank has come with. I have tried out other coils in tanks and not liked them but again is this down to my initial impressions and do I give other coils a proper trial? What I have found so far is that all the coils I stick with in tanks can all satisfy me at the same wattage so all my mods are set to between 50 and 60W which makes life easy! So my answer to your question is I favour the 0.4 coil on the Cleito but I may give the 0.2 a proper try one day (for a whole day). The 0.2 might just hit the juice and battery life too much although in my favourite tank I use 0.25 coils all the time and I haven't noticed any huge battery drain. I've read reviews that praise the 0.2 for the Cleito so maybe worth proper experimentation but as @vapemac wrote some report spitback. Coil prices and availability also come into play but I'm not sure if Cleito coils are different prices. Find the coil you like, stick with it and consider stockpiling just in case ... (TPD looms).