I have been through:

-- Conti T&Cs on an MTB converted for touring (a while ago, I must note because the model of tyre appears to have changed). Big, chunky, OK for occasional offroad, but generally a bear to push along all day with a load. They had a reputation for lasting a long time, especially those originally produced in Germany; the Asian-produced ones less so. The inverted tread apparently was good for snow riding at lower pressures.

-- Vittoria Randonneurs, which in 700x32 were standard fit on the Fuji Touring when new. They were an OK tyre for on the road, but a bit of a gamble on gravel. They were outstanding for longevity. I had few flats with them.

-- Conti Top Touring 2000s in 32C profile which were on the Fuji for ages (with several sets) for touring and commuting. I found them to be very good, and while I can't remember the distances I got out of them, they lasted well, handled well in most conditions and didn't hassle me too much with flats until the tread was almost worn away.

-- Conti Ultra Gator-Skins in 25C size which I converted to for randonnees and general touring. They were an OK tyre, with plenty of durability, good handling, good flat resistance. I never really ran them at the recommended pressure, either... lower to ease the vibration through to the butt and hands.

-- Vittoria Rubinos in 25c size. My favourite bike shops, for some reason, went away from Contis and to Schwalbe and Vittorias. Again, for randonneuring purposes, I went with the 25C. The Rubinos, with a "flat" cross section when deflated, certainly improved the handling (or should I say feel) of the Fuji over the Conti Gator-Skins. Their longevity also has been good. I went with them on the fixed-gear for randonnees and our European tour last year.

-- I have just returned the Fuji Touring to its dedicated duties as a touring bike, and fitted Velocity Dyad 36H rims and Schwalbe Marathon XR tyres in 32C size. At the recommended pressure, the tyres certainly give the bike a lively feel, but I did have trouble seating them on the rims initially. The first 15kim ride yesterday wasn't enough to give an accurate opinion of their longevity, of course, but we shall see.

I ended up going for the Schwalbes for convenience retail-wise. I did reconsider the Vittoria Randonneurs, but the shop had only one of the 32C size I wanted. One thing I did notice in researching the Contis, however, is the wide variation in the Threads-Per-Inch count on their tyres, and how the supposed long-distance trekking, touring and commuting tyres generally had a lower TPI than the others. Perhaps this has to do with the lower pressures the tyres run compared with their racing counterparts, but I also think the lower TPI means to a certain extent lower quality.

Contis also are renowned for overstating the size of their tyres, and certainly the Schwalbes fill a bigger space between the chainstays and forks than the Contis ever did in the same 32C sizing.

If you only have T&Cs as your touring tyre, then go for it. But I'd much rather a 26 x 1.5 or 1.75 slick. At the moment I am running Specialized Nimbus in 1.75 version on my commute bike over a mix of gravel and bitumen road, and they are doing well. My advice would be to opt for them if you are running 26" rims.