It's a common question these days for people new to the structured content development paradigm/tech publications world. Here's the simple answer:
- If you have to do a lot of parts related tracking and also integrate with servicing related information, go S1000D. It's really the only thing out there with the muscle to get the job done. (by the way, you may be required to go S1000D by a government agency – so that makes the decision easy)
- If you need to run a website full of all sorts of different kinds of information – that generally does NOT require keeping track of a lot of parts and what they fit into – then go with DITA.
Yeah, it's really that simple. DITA is incredibly flexible and there are some great tools out there to help make DITA a real workhorse in your business (check out our SDL Trisoft solution). S1000D, because it's a more prescriptive approach to getting something big done (like documenting aircraft, tanks, trucks, cars, ships, submarines, field hospitals, aircraft carriers, etc) is a bit more challenging, but truthfully, it's a lot easier to implement than DITA.
Basically S1000D tells you what to do and how to go about doing it – with a fair amount of analysis and design decision points built into the spec known as S1000D Business Rules that make it easier to figure out what to do for your specific situation. DITA leaves a bit more head scratching since you commonly need to build your own set of schemas (though there are some generic starting point schemas you can pick up, you generally need to do a fair amount of data modeling to get where you want to go). DITA does have one significant advantage – there are a lot of DITA books out there and a fair amount of available expertise you can get your hands on quickly in order to get started.
If you compare the earlier versions of the two specs, DITA about three or four years ago had a spec about 200 pages long (before you DITA geeks get too excited, yeah, I do know about all the other papers written to go along with the spec, but those don't really count since those were generally about how to build a system to compile the data and identify if you're DITA compliant). S1000D has been in the 2,700 to 3,000 page realm for nearly six to eight years. Granted, there are a lot of books on the subject about DITA and basically only the free specification for S1000D on the www.S1000D.org website – there are no available books on S1000D just yet, but I expect there will be soon enough. Each has a wealth of information for you to plow through. Each has its challenges. Each has its faithful followers.
I lean toward S1000D because DITA could learn a lot from S1000D (and has). DITA faithful have even created S1000D like implementations (isn't imitation the most sincere form of flattery?). S1000D implementers dream of the flexibility of DITA, but understand why they're locked into the S1000D "standard". That's another thing that separates DITA from S1000D. Basically, DITA is a free form do what you want kind of standard, a "here's how you can go about doing it" approach (can I even venture to say it's a "theory Y" approach?). Where as S1000D is more "if you're going to use it, you must use it this way – OR ELSE!" (I can definitely state it's a "theory X" approach – but sometimes that's a really nice way to make things happen) That's what really separates the two specifications. So, if you need a prescriptive approach, go S1000D. If you want to make a lot of tailored and unique data models, then go DITA.