CAD vendors have been introducing toolsets that allow users to approach design directly, either in conjunction with, or as a replacement to, traditional history based modeling techniques. Without explaining the History of CAD, or arguing which technique is superior to the other, let's set a parallel technology comparison. It is easy to find many technologies that can be compared to that of the direct modeling/editing versus the history-based approach discussion.
For example, Apple and Microsoft have been competitors for over 30 years and have many similarities to this battle going on in the CAD industry. Apple, in today's market, is focused on convincing consumers to "switch" to their computers, touting power without complexity. While Microsoft, on the other hand, has been the standard everywhere, especially in business, and has gobbled up over 90% of the PC market. If you had to generalize the markets or areas of expertise for each of them, and there are many to choose from, you might believe that Apple's stronghold is in the artistic and media production industry (Print/magazine layout & design, picture/movie editing & production, creative markets). Microsoft, for the past 20 years, has been the ubiquitous business software company, delivering high end, powerful enterprise and IT infrastructure solutions. While powering much of the corporate world, Microsoft offers a seemingly unlimited list of applications from which to choose. That being said, it would be foolish to assume that if you use Microsoft products, you are unable to be creative; or that using Apple products limit your ability be productive in the corporate world.
Direct editing, like Apple, brings powerful toolsets to CAD, helping engineers and designers conceptualize creative ideas and verify fit, form and function without investing the overhead of approach. History-based tools, on the other hand, have been adopted as "standards", similar to Microsoft, and are powerful platforms from which many of today's products are designed. Most might also agree that the direct modeling (DM) approach is more intuitive and easier to understand at first glance than history-based (HB) modeling. However, the power of history gives the user insight of how a model was built and the ability to apply explicit rules that impact future features.
The important point is not what technology is better, but about providing tools to get the job done. There still might be a point to be made on which execution is best or what mix of DM and HB tools can give the best approach options to the user. Currently, direct modeling is offered as an interface communicating to a parametric model (SolidWorks Instant3D / Pro/E Wildfire 5), a hybrid approach within one CAD platform (SolidEdge Synchronous Technology/Autodesk Inventor Fusion), an integrated toolset (Catia V6), or a separate CAD platform all together (SpaceClaim). Every CAD vendor will argue that their approach is best, but like every technology clash (Apple/Microsoft, HD DVD/BlueRay, Direct Modeling/History Based Modeling), the consumer will choose which product or toolset best addresses their design challenges.
In the same respect, I own an Apple MacBook Pro not because I think Apple's operating system is superior to Microsoft's, but because the Apple's hardware allows me to run any operating system and grants me access to any application. In the Apple/Microsoft decision it is all about the applications since that is where the real work is done. Similarly, direct editing and history-based modeling are application of CAD, each with their own function.
Personally, I use SolidWorks extensively, as you may have guessed, so I understand how Instant3D allows the user to edit parametric data in a way that feels direct. I have also tried SpaceClaim a dozen times in the past 2 months (mainly to understand pure direct modeling), however I am not designing products everyday nor do I have deadlines to meet. In order to shine better light on this discussion, I would ask that you comment on which implementation of direct modeling/editing would work best for your applications. ~Lou