[mtdewcmu]

If you're going to write shell scripts or do anything sophisticated with the shell, it's worth understanding the difference. And there is a fundamental difference. With |, standard input is hooked up to a pipe. With <, standard input is hooked up directly to the file. Sometimes it does matter.

[isolate]

The purpose cat serves is that it lets you forget about < until you really need it.

[throwaway999888]

The comparison was between cat + pipe and < ...