I'm wondering which one will be more valuable and have more career opportunities. Web usability or web accessibility. Please show statistics or any valid information if possible.
So the winner is accessibility!
Might be of interest :
Edit: I feel the topic is a little heated and there are two main positions:
Anyway, I think one can see it in different technical, practical ways, too. If one reads the job positions carefully its quite obvious.
And, I still believe in the stats I sourced. Even if here isn't the audience of the winner side, but they look quite significant for me. Nowadays, you are downvoted only. Not killed ;) I believe developers are much more searched and needed and higher paid than designers. Even If I'm a believing designer, too.
Accessibility is part of usability. It's more commonly discussed because the US has official accessibility requirements that must be met to comply with ADA regulations.
Anecdote: I make UX hiring decisions. Having worked at Google, LinkedIn, Groupon, and two startups, we have never hired someone whose title was "accessibility" anything. We have hired lots of Usability Researchers and UX Designers, both of whom are expected to be aware of accessibility issues, design for them, and test for them. (Designers typically have the most ownership at the level where accessibility is planned for and implemented — they'll work with the engineers to make sure those concerns are addressed at several levels of the design.) Engineers also have to be aware of these issues — you can't really roll it into one person's job, because to truly make a site accessibile, everyone throughout the product development stack has to be thinking about it.
Try searching LinkedIn and other job sites for roles with "accessibility" (1,200) in the title versus "usability" (2,300). My search (http://goo.gl/ykFnm) resulted in very few job titles with "accessibility"; if you search "usability" you can see that it is considered big enough for its own job. Accessibility is mostly not a skill that is big enough for its own role, except in the largest of companies or government organizations.
Either way, you're going to make yourself a much more valuable employee / consultant if you generally know about usability analysis and research and not just accessibility.
To create truly great user experiences, one must understand how these, and many other disciplines work together. While some disciplines are co-dependent like usability and accessibility, others are traded off like usability and visual design.
The pioneers (Nielsen/Norman) of the field define user experience as, thus
Having said that, usability and accessibility isn't one singular discipline, and any job that advertises as such, have a fundamental misunderstanding of what usability and accessibility is.
Interaction designers, user experience designers, information architects, usability consultants... all those job titles... while you may be more specialized in one aspect than the other, they're very closed related, thus allows for a lot of horizontal mobility in the field.