A USART is a universal synchronous asynchronous receiver transmitter. A serial port if you like. On the STM32 however, it really is universal. This peripheral has a raft of features for a huge range of serial protocols including all the usual asynchronous modes plus IrDA, LIN, Smartcard Emulation and the ability to function as an SPI port…
In general the dsPIC is well blessed with peripherals. The dsPIC30F6015 I am using at the moment has two serial ports in addition to a couple of SPI ports and an I2C port. These UARTs seem pretty easy to use as well. Still, like other peripherals on the dsPIC, they still found a way to catch me out. My own fault for not reading the data sheet properly. The trick here is to realise that there are FIFO buffers associated with the ports.