a table that provides a side-by-side comparison with M8
8 is a truly great system, and definitely probably the first really big GIS to successfully provide a "something for everyone" package. For all that, 8 also has many features that are rarely, if ever, used.
9, in contrast, has had a much greater focus on building out features that come in sets to fit specific use cases, as driven by the community. Given that the first huge set of capabilities 9 provided (which 8 does not have) revolved around the core, data-centric infrastructure of the Radian engine, those people who were early adopters were the community driving all those features to a very high level of completion and refinement.
Those folks were demanding all those features because those features are essential to ease of use, efficiency, and convenient operation in the work they did. 9 is absolutely the smoothest, most powerful, easiest to use tool if you're slicing and dicing GIS data from a data science, IT, ETL, DBMS perspective. It has a great set of point and click transforms for all that, the interfaces are smoothly orthogonal, you can mix point-and-click with expressions, with SQL, with scripts, and even get previews in cases where other systems force you to cut at your data blind. All that is a testimonial to community feedback where people doing such work steadily and regularly sent in their suggestions and comments.
Starting last year and moving into this year there's been a much greater emphasis put on interactive GIS, which all makes sense. Every time 9 expands the interactive feature set in some area, that expands the user base in that area and those users naturally push for more features in the areas they use. Given the expansion of interactive features for things like style and editing that's really picking up with way more focus in those areas.
But the key thing is not to waste time making matrix lists comparing one system with 5000+ capabilities to another system that has 5000+ capabilities (9 already is very large), it is say what you personally want for your work. We can't all be experts in what other people want, but every one of us is the authoritative expert on what we want.
The most useful way to express that is with "top 5" and "top 10" lists. Mike Pelletier, for example, has contributed lots of insights in the form of compact, consistent lists of top priorities. Besides being clear statements of priorities, such lists are much easier for us ordinary humans to cobble up than universe-wide theorizing that covers very many areas or features at once.
In my personal work, for example, the volunteering I do, I do many projects in 9 that span a fairly wide range of GIS use cases. I always have a 9 project open on the side that is a table of suggestions I want to make based on the real-life work I'm doing (I use 9 as a personal information manager and project manager). That project usually has small things but sometimes bigger things. Things like being able to hide and show fields in tables was one of those.
A recent suggestion I made was an extension of that. I don't like it how in the Transform pane when you have a pull down list of fields it shows all the fields in a table. Instead, I want that pull down list to show only those fields which are not hidden, with a more... choice at the end to show all fields. Why? Because when I work with tables that have dozens of superfluous fields (like those in the Natural Earth data sets) and I'm only using four fields out of fifty, I don't want all the other 46 fields cluttering my pull down menus.
Little things like that add up, and because they are compact and specific, they are easy to suggest. Taking that approach for bigger things also helps. For example, it would be great to have scale bars, but in my view that can be done in two steps: I'd like to have a very basic, one style scale bar done right away, because that covers many of my use cases. A second step to add to that a more expanded set of default choices would be good, and then maybe in some future release the ability to customize, or maybe not.
It's true the approach I'm recommending only works for people who have learned 9 well enough to know what is in it, what works with super ease of use and efficiency, and what needs improving. I don't think that's a bad thing, because whether it is tools for carpentry or a better winch handle for a sailboat or a new edit mode in Manifold, I think you get the best insights for ease of use plus super capabilities from people who actually use those tools.
So... as you get more familiar with 9 I'd strongly recommend sending in short lists of your top priorities for more global direction, and get in the habit of regularly sending in small suggestions as well for various small details as they come to mind. It's all good.