connecting a 4 inputs hub (connected to devices as external tv tuner,external soundcard, external hardisk, mouse) to a usb port of a desktop will be the same as connecting the 4 devices directly to the 4 usb of the desktop(as speaking of speed?
Speed wise yes a hub would be slower.Because it's like plugging 4 USB devices into 1 port. Weather it would be noticeable or not I don't know. Just leave the things you use all the time plugged in to the back of your computer and everything else in the hub when you need them. Simple