Is there any advantage of choosing a long board version like below over a PDCB?
Also, for a general good practice, is it better to choose both the PDCB and the power brick of a same output wattage? Or is one supposed to be of higher wattage than the other for some safety reasons?
I would not choose a long board version because then you are concerned with mounting it. There is a small cost savings. Long board version is also easier to engineer higher specs or a wide input.
The output is only good up to the weakest spec link, so choose as your budget allows.