Aaah well... you might as well ask Shimano or Campy? Marmite or Vegemite? VHS or Betamax? (the last one was for those of us who are older)
Just my opinion: I don't think it really matters for the vast majority of us given the touring we do, and not for material riding characteristics. For riding characteristics, what really matters is the frame design, the components you use and your attributes and riding environment. I've used frames of different material with undesirable characteristics in both. Material is by far from the sole factor in how a frame behaves; there's too much else that comes into play.
Concerning repairability, I also don't put too much stock in this. Sure steel is better for repair, but let's ask this question: the next time you are touring and your frame breaks, what would you do? (assuming you survived the frame breakage or failure that is without a tour ending injury!) What if the frame broke because of rust? Would you want the frame still repaired anyway? If it's in a country where welders are few and far apart, would you trust the repair? Could you even find a welder who is skilled enough for a bike frame? Would it even be within a 30 mile radius? Let's even say you could find an appropriate welder close by -remember that the repair will result in paint damage -which is costly to restore, too! Would it come out cheaper than buying a cheap bike and putting racks on it? (I'd also bet you can find more places that sell bikes than welders, too). Let's not also discount the fact that you could even get a bike (or frame) shipped to you in many places -and those places that are so remote probably don't have welders in that next settlement over the hill either. One last point: what if your frame is warranteed? Do you think the warrantee would hold given a non-specialist welder getting their hands on it?
Of course, there are times where having a frame that is repairable is an absolute advantage -however, my thought is given what you need for a repair and the likelihood of finding it, I'd take the risk of getting a decent non-steel frame and components (regardless of the material!).
For full disclosure: my touring bike is steel, but I'd also be quite happy with any decent quality touring frame of any material. I also tour in "developed" countries and if my frame ever broke, I'd either buy a new bike to continue or rig up a fix if it was a rack eyelet.
.
(sorry, just had to add that)
