The Serow bike compared to the TTR occasionally crops up on this forum. Having personally started green laning on the Serow a few years ago I later moved to the TTR.
At the time I had recently read both of Lois Price books, the first when she used a Serow and the second when using a TTR for long distance rides.
The following is a copy of an email Lois sent me which may be helpfull.
Hi Colin,
Thanks very much for your message, and of course I'm very happy you're enjoying my books! Thank you for letting me know.
Interesting question about the Serow to TTR250 move! I think the TTR250 is probably that little bit tougher and nippier than the Serow - it certainly fared incredibly well on my Africa trip and is still going strong(ish)!
The Serow is great because it is so low (as I am short) and I did lower the TTR, which probably spoils it geometry somehow. I am considering a new bike at the moment and will probably go for another post-2000 TTR (the blue one) again. Although I would consider one of the new Serows (the 250cc ones) but they go for about 3000 pounds so a bit out of my price range. I have ridden one and it was great!
So, I would say if you are reasonably tall then the TTR is great and good value for money, super reliable and easier to get parts for than the Serows (which were all grey imports).
Let me know if you have any other queries - I have fiddled with those bikes rather a lot!
Hopefully see you on the trail some time, or maybe I could come up to Cumbria and give a talk to you guys about my adventures!