I'm curious about this. My friends told me that there is difference between the speed of internet connection when you connect your PC/Laptop with Bluetooth or USB cable. They said that the internet speed is on good speed when you connect the mobile with USB and the speed will low when you connect through the Bluetooth. So does it really true? I want to know if YES then why it is?
It just depends on the version of USB or Bluetooth that you are using. You internet speed will become limited to the bandwidth of BlueTooth or USB. On Bluetooth you will have the free air factor(the propagation of signal will be suceptive to signal interference from random noise, instead of USB, where the noise is high limited with twisted metalic pairs).
USB 1.0: Released in January 1996. Specified data rates of 1.5 Mbit/s (Low-Bandwidth) and 12 Mbit/s (Full-Bandwidth).
USB 2.0: Released in April 2000. Added higher maximum bandwidth of 480 Mbit/s (60 MB/s) (now called "Hi-Speed").
USB 3.0 has transmission speeds of up to 5 Gbit/s, which is 10 times faster than USB2.0 (480 Mbit/s).
Bluetooth v3.0 + HS (most common): Bluetooth 3.0+HS supports theoretical data transfer speeds of up to 24 Mbit/s, though not over the Bluetooth link itself. Instead, the Bluetooth link is used for negotiation and establishment, and the high data rate traffic is carried over a colocated 802.11 link. Its main new feature is AMP (Alternate MAC/PHY), the addition of 802.11 as a high speed transport.
Even if you look at theoretical speeds, USB 2.0 can get a max of 60 MB/s while Bluetooth 2 can barely hit 0.32 MB/s.1
1 I converted the speeds from Mbps (Megabits per second) to MB/s (Megabytes per second) because that's usually what people care about when it comes to downloads speeds.