I think they each have different characteristics. Those characteristics are based on marketing to markets seeking to capture the greatest market share(s). It could be shares because of the many, many markets or audiences today.
I prefer one over the other for different purposes. I began using Netscape. I think it has gone to the wayside now. I feel Firefox offers more freedoms of tailoring my browser and browser utilities. I like Chrome for fast searches particular to SEO techniques and connections. I use Bing when I wish to see more 'common' results. I use Google a lot because I know how to use the advance features for searches.