Large technical manuals may require special handling, so the tool used to write the manual can become very important. Should you use Word or Framemaker for very large manuals? The answer depends on several factors which I will discuss here.
First, lets look at some of the pros and cons for Word and for Framemaker.
Word is a well known and widely used program. This alone gives it a strong advantage over Framemakerin many cases. It is feature-rich, and relatively easy to learn. Word is very strong with marking up documents using comments and highlighting, which is extremely useful to track missing or inaccurate content. So if you have Word and you know how to use it, why would you not?
There are several serious problems with Word. It is horrible at handling large files for a start. As your manual gets longer, and especially as you add images, Word can become very slow and even crash. Images can do odd things like float to the top of the page or engage in other undesirable self-formatting exercises. Once a file reaches a certain size, it really needs to be split into several smaller ones. Word lacks automated page, section/chapter and other numbering features across files, and forget about cross-references across files, so if you need to split up your manual, there will be a lot of manual work to make up for these shortcomings. Not only is this time-consuming and error-prone, it is horrendously tedious. Errors and hair-pulling multiply as changes to the document require updates to numbering and cross references etc. across files.
One horrible fault that Word has no matter the length of the document is ordered lists. If you want to format the numbering, and if you have several levels to the list, Word becomes a real beast to tame. This has been a problem over many versions, and it has actually become worse, not better.
Framemaker is more or less everything that Word is not: it is hard to learn, other than companies with a history of writing large manuals, it is not commonly available, but it is very strong at handling multiple files as a single document and has very flexible numbering and cross-reference features.
Once you know Framemaker, it is easier to use than Word in many ways, because you get what you expect. It tends to lack some of the nice productivity features that Word has, such as programmable keyboard short cuts, but makes up for this by handling arbitrarily large documents across as many files as is needed. I usually make each chapter a separate file, occasionally splitting a chapter into two or more files if needed.
Which is Best to Use?
Having discussed the pros and cons of each, which is the best tool to use, Word or Framemaker? The answer depends on a couple of factors. If you are in a contractor-client relationship as I generally am, using Word is often a better choice over-all because the client can tweak the manual as needed. However if the manual is really long and full of illustrations, Word simply may not be practical and it may be necessary to use Framemaker, even though this prevents the client from making modifications themselves.
Framemaker wins when manuals are routinely very large, especially if the client already has Framemaker in-house.