I will go with the gtx1660 super instead because of long life span, trusting two or more things is better than trusting one thing, if the RTX3090 fails it's overs, if one gtx1660 super fails you still have three left, more hope I believe
If cooling is all that RTX 3090 needs I'm here for it, i prefer mining with one RTX3090 than more GPUs, it makes things look cleaner and again a single RTX 3090 can do 120mhs but at least wattage consumption, 4x gtx1660 will draw 320 watts and a single RTX 3090 will draw just 290 watts