My 5 cents thoughts about it:

The Yamaha WR is better when it comes to weight as it is around 14-15 kgs lighter. Its better when it comes to power as it has 30,7 HP compared to the CRF that has 23 HP. The stock suspension is also of higher quality on the WR compared to the CRF.

The WR has also been longer on the market so theres more aftermarket alternatives although the CRF has out a few years now too and aftermarket stuff are probably readily available for it too. The one thing I have noticed is that the biggest aftermarket fuel tank for the Crf is the Acerbis 12,5 liter whereas I think you can get a 20-21 liter fuel tank for the WR.

When it comes to reliability Im not an expert at all but in general its hard to beat a Honda. But the Yamaha is probably great too.

Another factor that might count in - youre going to Asia and Southeast-Asia maybe? The Honda CRF are made in Thailand, and thus parts, accesories, tyres are readily available there and to a certain extend in neighbour countries, and bike mechanics that know that model well are "everywhere". The CRF are also sold in Malaysia and I belive to a certain extend in Cambodia and Laos too.

There is a welsh woman going RTW on and CRF and a dutch couple too - on two bikes of course. So theres someone to get in touch with and get first hand information and experience.

I think a 250 bike is a very good choice through Asia.

__________________
In the end everything will be fine. If its not fine its not the end....