BMW G650 X-county vs XT660 vs anything else

[Jtw000]

I'm taking a ride from London to Bangkok. Once in Bangkok I need a decent commuter to mooch around on for 6 months and before I go myself and partner are spending a month going around Europe so I need one bike that does it all. I'm trying to decide which is the best bike for me, I've got a list so here is my thoughts.
I have had a lot of bikes over the years so have plenty of experience with different kind of machines. I currently have a BMW G650 X-country, I bought that for the trip last year, I've had it a while now and really like it. It's been reliable and never misses a beat. It's a little bit smaller than i would like and could do with it being a little bit more powerful but it does the job. I've been working out the costs of getting it ready and frankly, it's prohibitive. For the money to do it right I can literally buy a trip-ready machine. I've been offered a Yamaha XT660 which I like but the price on that particular one is too high, they can be had pretty cheap. I like the X-country but to correct the know shortcomings is a lot of money I really can't warrant, (£1100 for touratech steel rear subframe and panniers, £300 for a decent rear shock, DID chain and sprockets, etc, etc). The XT is not as cheap to run, is heavier, dated design, basically a commuter with an upright seating position but it will keep on running and is easier by a long way to work on if something goes wrong. Also the parts are a fair bit cheaper, I can sort the luggage out for half the £1100 that it's going to cost on the BMW.
I know the F650gs has had its issues but then what bike doesn't. With a free choice I might well have gone for a Dakar. My X-country is the 07, built in Italy not china so is taller in the saddle and arguably more reliable. I am on various forums and apart from one notable rear shock failure and a few snapped subframes they seem pretty hassle free which has been my experience.
The BMW has a certain quality to it and is a nice bike to ride. I worry that if I go through all this with an XT it will still just be a bike to me as I'm really not a fan of them.
Does anyone have any experience or suggestions.
Thanks.