Both are good, if you are going for RTX3090 make sure you buy better brands with three fans and good thermal pads tweaks, you can watch youtube videos about best RTX3090 cards available on the market, I just find the 1660 Ti and super to be extremely quiet and cool
LOL if you pack 1660ti together they ain't cool no more and you can add the trouble of managing 4 pieces of them.
go for 3090..what is this bull market for?
It's not hard to manage 4 GPUs at all, I have 6x 1660 supers and they mine at 31mh each at 54°C per one, they are all Zotac brand with just two fans, try getting that temp on a RTX3090 and you will be the difference