This question already has an answer here:
Is there an advantage, that Canon or Nikon's entry level dSLRs hold over their competition ones (notably Sony) for a young enthusias who wants to learn more but is currently, and probably won't in the immediate future, not interested in investing too much in lenses, apart from the starting one and maybe one with that.
More interested in technique and composition.
Edit: mattdm beautifulyl put it in the comments below, so I'll just steal his words. Apart from being able to upgrade indefinitely into the ecosystem, what would be the reasons for choosing Canon/Nikon entry level models?