The central appeal of an integrated amplifier is the chance for a designer to maximize the synergy between internal systems: the preamp that best fits the amplifier.
Unfortunately, most integrateds are not designed with synergy as their guiding principle but rather squeezing as much into a single box as budget will allow.
I think of most integrateds in the same way as an all-you-can-eat restaurant. Lots there, not much is very good.
There are always exceptions.
One of the beauties of separating the integrated’s internal systems is the power of the upgrade. If you take the time to source synergistic separates you also benefit from the ability to upgrade some pieces and not others.
Integrateds make it easy and make sense if you trust the manufacturer to put their hearts and minds into the product.
For the most part, go separates.