There are advantages of both. Discrete circuits can be made for some special characteristics (such as very high voltage or lowest possible noise for some given source impedance), or customized with features that just don't have enough of a market to interest IC designers.
But there are some things that can be done in integrated circuits that just can't be done in fully discrete circuits, such as extremely high inherent transistor matching and highest possible thermal coupling between devices that need to track to work right.
But there are some things that can be done in integrated circuits that just can't be done in fully discrete circuits, such as extremely high inherent transistor matching and highest possible thermal coupling between devices that need to track to work right.