You are in your twenties and have still to start working, why would you chose a platform over another ( even right now )? I would learn both and move on jobs to make almost equal experience over them.

Else you will end using the only tools you know over the best tools for each specific problem, and it can be a disaster for you career and your satisfaction as developer.

I am not saying to be a jack-of-all-trades-master-of-none, you can still have (and focus on) a preferred platform/os/tools/etc for any reason (like you like it more, you have an ethical problem with another, in your zone one is overused compared to the other, ...) but, imho, is better to be something as a T-shaped person [ as described on the Valve handbook, page 46 http://www.valvesoftware.com/company/Valve_Handbook_LowRes.p... ].