What the FPGA dev board to choose: Xilinx or Altera?
Honestly: it does not matter much.

Both companies are about on par with


features: lots of lookup tables, some dedicated blocks like multipliers or I/O),
development environment (annoying)
pricing (all the good features are available only for serious money)


Deciding on a board without a very concrete project in mind is always difficult, so I'd pick a project and then decide on the board by the available peripherals on the board.

FPGAs only have digital I/O lines and a few dedicated clock inputs and outputs that can be used to synchronize communication with the outside world. If you need analog input, you need a separate ADC, for analog output, you need a DAC, and for USB you need a USB controller (the USB protocol cannot be sensibly emulated with just digital I/O ports).

Having a display is nice, but it will be difficult to set up unless you just use pre-made components -- but on the other hand it is a good learning experience because it has several stacked layers.

Protip: You can also add WS2812 LED strips as a peripheral easily.