A long time ago (15 years) I replaced an amp and a preamp with an integrated. I had a Belles Preamp and B&K amp, not "high end" but reliable and powerful. I wanted a remote for the preamp, and my main dealer said if I was going to replace the preamp, he had a deal on a Plinius integrated that was far superior to what I had for only a couple hundred bucks more than a new preamp. It also has a good phono stage that can accommodate MC carts (but I ended up getting a separate Sutherland Insight phono stage which improved the sound very noticeably).
Less cables with the integrated (although my phono stage eliminated that benefit) and all things being equal, they are less expensive because there is only one box to manufacture, one power cable to buy and no interconnect needed from preamp to amp. Unless I had some reason for wanting a different amp and preamp, I would only get an integrated. Some guys like more boxes and complexity - I prefer the opposite.