I come to that conclusion by comparative analysis and a bit of extrapolation... damn engineering degree makes me do it, sorry
XBMC, MediaPortal, and XLobby have simular feature set, simular purpose, and actually run on simular platforms. Yes, the XBOX is a PC and actually uses a mod'd version of MS Visual Studio using C++.
After using all the products it very easy to compare on a complexity scale.
They each have features that the other does not have but all in all MediaPortal and XLobby get to leverage the WinOS's built-in features and 3rd party apps much more easily... which means that XBMC must adapt or code a lot from scratch (they DVD player portion and others) just ot get features already built-into the OS. So in all this make is quite a bit more complex.
In the end Steven can do what he pleases, of course.
But his choices either make or break the software. When you bring more people into the fold you have the chance that it can get much better, much faster and compete with the apps that are already worked on by many devs.
I like XLobby and think it has TONS of potential! Steven is a great coder but he also has a life outside XL. In order for XL to even try to keep up growing at a reasonable pace (not even thinking abotu 'competing', just simply enhancing) it must allow other talented devs to help out.
XL has been at or near a standstill for a year or more IMO while all other apps have grown a ton.