Whenever there is a new market created, we generally see tons of companies flood to the market. Many of those companies fail to gain any meaningful market penetration and they give up. The market is then left with only a few players. An example of this is e-readers. Everyone had an e-reader but now we really have only a few that have any real market saturation. We are absolutely seeing this with the mobile OS space.
Making a mobile OS is obviously much different than making a desktop OS. There is much less pace to work with and people expect the OS to behave differently. When a new OS enters the arena, people expect their version to be much better or different enough to switch to that OS. The OS can also target a different socio-economic market or target of the market.
The problem with the current OS variants that are either out or are still in development is that they are way to late to the game. Android and iOS already dominate the high end of the market. iOS will never really target the low end because they expect their margins on their devices to be too high to compete in that space. Android and Windows Phone to some extent are penetrating the lower end and emerging markets. Android already controls China, which is such an important market for everyone.
The great thing about Android is that it can be released on lower end devices and it is open source. Anyone can use the OS on their devices unlike Windows Phone which is controlled specifically by Microsoft. Firefox OS and Ubuntu Phone OS have this feature as well but they are releasing at a time when Android has permeated so many areas. It is smart to target the emerging markets because at least either Firefox OS, Windows Phone, or Ubuntu Phone can be a second or third option for those markets.
Firefox OS has a leg up on Ubuntu Phone because the Firefox name is already recognizable. Ubuntu virtually has no recognition. I am not sure about how important the Ubuntu name is in emerging markets, but if it is similar to the US, then it is really non-existent. Ubuntu has been trying to compete in the desktop space for so long with no real gains to speak of. I bet even Chrome OS has more market share than Ubuntu on the desktop. Firefox OS is also taking advantage of HTML 5 for their apps where Ubuntu wants you to write native apps for their platform although developers can also use HTML 5 to develop apps. It is going to be significantly easier to write apps for Firefox OS. If HTML 5 is the platform that everyone wants it to be, Firefox can have an advantage over iOS and Android that want you to buy apps in their store. Firefox is the most consumer friendly. Whether that means anything to anyone is yet to be seen, although it is interesting. Ubuntu is running their desktop OS on the phone. This means that you could potentially plug in your phone to a monitor and run the complete OS. I don't really see this as an important feature because very few people run Ubuntu currently.
I read on www.techweekeurope.co.uk that Firefox OS already has deals made with lower end manufacturers for their OS while Ubuntu doesn't really have a partner. This could change but it really gives Firefox a huge advantage. If HP hadn't screwed up WebOS so badly, this may be a non-issue.