For touring I'd go with steel.... just about anybody can weld steel tubes. With TI you need a specialist.
And how many people break their frames on tour?
It's an oft quoted reason for going down the steel route. Just about anyone can weld/braze steel tubes but how many of the 'anyones' can do it well?
It just so happens that I've had steel frames break on my on two separate occasions. Technically it wasn't the frames but a rear drop out both of them on Dawes Galaxy bikes.
The first time was in Chorley on a Friday evening and it was brazed and I was back on the road within 1.5 hours. The repairer? Bill Nickson, the last British winner of the Milk Race. I lucked out on that breakage.
The second time, I was in Orleans. The bike was getting close to needing a new drive train and derailleurs, new rims and tyres and after factoring in a repair and restorative respray on my return to the UK I'd have ended up spending a lot more money than I did on an aluminium framed replacement tourer/hybrid bike that I bought from
Decathlon. I finished my tour on a near brand new bike and the Brooks B17 saddle from the Galaxy. Someone finding the abandoned Galaxy would have been able to salvage some serviceable cantilever brakes, a new Decathlon saddle, and a decent set of handlebars with bar end shifters and brake levers.