No matter how hard you try an external metal box with multiple inputs and outputs will always be better than a PCI/PCIe card inside a PC for recording
USB can't offer as low latency as a piece of well-designed hardware plugged directly into your PCI bus, at least in my own limited experience. This comes into play when doing music keyboard recording.
eg. I found it difficult to find a USB MIDI adapter that didn't introduce unacceptable latency (when trying to record new tracks synced in real time to existing ones). Edirol was recommended to me but even after tweaking settings for hours it fell short. I wound up buying a second-hand Creative X-Fi Elite Pro PCIe card and love it.
USB can't offer as low latency as a piece of well-designed hardware plugged directly into your PCI bus, at least in my own limited experience. This comes into play when doing music keyboard recording.
eg. I found it difficult to find a USB MIDI adapter that didn't introduce unacceptable latency (when trying to record new tracks synced in real time to existing ones). Edirol was recommended to me but even after tweaking settings for hours it fell short. I wound up buying a second-hand Creative X-Fi Elite Pro PCIe card and love it.