Originally Posted by lighthorse

grantman,
You can tour crosscountry unsupported on a bike of any kind. If you want to carry panniers, then a bike that has eyelets may be called for. Beyond that it just personal preference.
My first ever tour was the Southern Tier on my LeMond Buenos Aires with two heavily loaded rear panniers. The bike was completely stock: wheels, triple Ultegra gearing, and I used 700X25 tires. It worked fine.
For my tour this year I purchased a "touring" bike and loaded it with two rear panniers. This bike is much heavier than my LeMond and therefor requires a lot more energy to get it up the mountains. It also uses XTR/XT drive train but I used a much smaller cassette than came stock. I do believe that if it were to be run over by a small car it would come out of the incident just fine. Do I "need" the touring bike to tour? NO. But I want more bikes so now I have one more.

I note that you are looking to use four panniers thus requiring eyelets both front and rear. Before you make that decision you might take a hard look at how much stuff you absolutely need to tour. Most of us take way more stuff than we ever need. Look at the size of some of the panniers and imagine how much stuff you can put in them. You may not need four.