Either has its advantages and disadvantages. Those have been well-listed by many posters here. If you are talking about sound quality alone, Integrated amps have narrowed the gap between them and separates. The high end ones are quite good and should not be dismissed. In the $10K range, The Absolute Sound recommends the following:
Bel Canto EIX $8500
Aesthetix Mimas $9000
BAT VK80i $9995
Technics SU-R1000 $9999