No DC is POTENTIALLY quieter. DC heaters cures only one kind of hum, and if your unit doesn;t have that issue, you will get no improvement.
I am not sure how you mean DC heaters is a money saver, after all it requires more parts. You mostly see it on circuit boards because most amps are on circuit boards. It matters not how you wire an amp, circuit board, eyelet board, point to point, you can wire the heaters with any method you like.
If you want to wire them DC just as a preventative measure, go ahead, it sure won't hurt anything.