Jolla has a better appeal I think. Firstly it's a full pledged Linux, not limited to JavaScript applications only. Secondly one will be able to run Firefox OS applications on Jolla as well, since the browser there is using Gecko.
Jolla also inherits all the problems associated with desktop Linux and it would also have most of the same problems that Android does (fragmentation, upgrade cycle, etc...).
I like the Firefox OS concept because it has a better chance at being popular amongst non-technical folks and because, even if it had like 5% of the market share and no more, even so it would bring benefits to everybody, including developers, including end-users - because those Web APIs are also pushed by Mozilla for standardization.
What are those problems inherited from desktop Linux? I don't like the concept of limited systems like Firefox OS (for me personally) since I prefer more flexible and feature rich systems, but I see nothing wrong with them in general, they can be useful in some cases.
The discussion above was about the huge geek appeal, not about the general appeal. That's why I answered that Jolla has a better geek appeal. Although they work hard to address the general public needs as well, in order not to make their system targeted to the tech crowd only.
Unlike Ubuntu, Sailfish uses the conventional middleware stack from Mer (i.e. graphics wise it's Xorg with plan to move to Wayland). Applications wise I can't really yet compare, since there aren't much details on Sailfish before it will be published. Hopefully it will be open sourced together after the launch (I mean the default applications like e-mail client and the rest). Silica UI components are open source already.
