Not sure you understand what is going on.
You are only talking .2w difference. There was something going on with the 2.5 coil. Maybe pushed to one side or getting clogged up.
My preferred vape is about 7w and no matter which coil I'm running the vape is real close. Fruits I may back down to 6.8w
2.5, 1.8, 1.5 should all yield near results at or near a predetermined wattage.
Im talking about the warmer vape im getting from the lower ohm coil. Ive gone through 4 or 5 2.5ohm heads and they were all a cooler vape even at a higher wattage, even tho it is a slight difference. I moved it back up to 6.3 and its not burning on me with the 1.8ohm at this point. The range in ohms on the heads all create a different circuit, as the lower the ohms the higher the current. This also means there is something physically different about the coils (thicker guage, shorter length, etc)
I couldnt get my protank 2.5ohm over 6.4 without burning, i havent tried with the 1.8ohm, i feel like burning flavor means my head will fail faster, so i try to avoid it at all costs. Definitely like that the vapor is now noticeable warmer and i feel like im getting a better pull, could be imagination on the pull but not the vapor temp, which is obviously slightly warm
Pretty sure my juices burn easily as ive never been able to hit the wattage others use with the same devices. I tried a couple different vendors but the same result. I do tend to take 6-7s draws, and have tried 6.5W but it starts to burn on pulls over 5ish seconds.