Basic Module

I was wondering what the advantages were of using a BASIC (co-processor) module for printing istructions.

I use AD PLC's and print directly from the CPU. The printer is only required to print about once a minute or when a change in the process occurs.

Everything appears to work OK, but I am not sure if this is the best way to do it.

The co-processor adds a second CPU and memory, to take the burden off of the main one. If printing from ladder isn't causing speed or memory problems, then you should be okay.
In this case, it sounds like the cheapest way is the best way.

Printing formatted text is MUCH easier with a BASIC module than it is with just the limited ASCII commands in virtually all PLC's.

I use the 260 CPU and the 06 PLC for printing to serial printers. I found the instructions in both to be far easier to implement than the BASIC co-processor. As long as your scan time isn't hurting you and you haven't run out of program memory keep doing what you're doing. Now if you're talking about a 250 CPU or an 05 PLC then the ASCII instructions aren't nearly as good and the basic module can make life easier.