The DP1.4a supports maximum 4K at 120fps, everything above that is using DSC (display stream compression).and if I am not wrong adds a bit of latency and a bit of processing overhead, because your GPU has to compress the frames. Additionally the compression adds some loss to the equation, but according to reports it is very hard to distinguish it from the lossless picture.

It is not a big deal but it is nice to have support for DpP2.1. DP2.1 has more than double the bandwidth of DP1.4a, meaning that it supports 4K 240fps, introduces FEC (forward error correction) and improves the HDR quality.

The bottom line is that if I shed north of 1K I would like to get something which is future proof.