UART from MCU using USB to RS232 converters are good enough to send data at real time to PC as MCU's are very slow in data sending compared to PC. I used it myself in some applications.
But it is also fine to use AR90USB162 as the USB controller is built in. But u have to develop USB driver for both microcontroller and PC. USB has one constant data rate mode called isochronous mode, for real time data sending/receiving, but u have to create a custom USB driver for that bcoz HID USB driver supports only bulk/interrupt transfer mode. And HID driver is free too. I remember using microsoft jungo driver development tool for USB isochronous mode. At the same time, u have to make a schedular for ur microcontroller with USB data transfer given a higher priority than any other task in microcontroller. This is kind of an overkill for 8-bit MCU but with few trial and error it will surely work along side ur application.
(https://msdn.microsoft.com/en-us/library/ms894725.aspx) gives some info on USB modes.