First of all, you have to determine the type of cycling you'll mostly be doing and how often you're really going to be doing it. A touring bike operates best, whenever loaded. You wouldn't attempt to win any road bike races with it against a bonafide road racing bike. All touring bikes have triple chain rings and include a "granny gear" for climbing hills. Something that you can better appreciate, once attempting to climb a hill while carrying over 70lbs of equipment.
If you plan on doing any touring that involves camping, then you're going to be carrying a heavy load, that will include cooking utensils, sleeping bags, a tent, and accessories. CX bikes were NOT built for such loads. Touring bikes operate more efficiently, when loaded. Touring bikes have a longer wheel base and their bottom brackets are closer to the ground for a lower center of gravity. Therefore, a cyclist can feel more relaxed by distributing more of his weight across the frame of the bike and will have a greater sense of stability whenever moving while loaded. For longer distances under load, a touring bike is the most appropriate tool for the job. Of course, for the quick weekend jaunts carrying light loads and staying in hotels, a CX bike can handle that type of credit card touring, with relative ease. In fact, just about any bike could. That would mostly depend upon the type of terrain upon which you'd be cycling, and the types of hills you'd be climbing. Touring bikes are really more versatile than CX bikes, because of their carrying capacity. Otherwise, a CX bike would be the better bike in terms of handling, responsiveness, and speed, under normal circumstances. That's whenever comparing an unloaded touring bike with a CX bike. Of course, once the bikes are loaded, the touring bike wins hands down!
Bicycle sizes can be different from one bicycle company to another. A 56cm made by Trek, could very well be a 54cm made by Surly. Therefore, bicycle sizes don't directly translate from bicycle company to bicycle company. It's not too advisable to go by whatever a bicycle salesperson says about the "correct" bicycle size for a customer. Sometimes, they're only trying to reduce inventory as fast as possible. The best way to determine your "proper" bicycle size is thru a "proper" fitting. However, there are plenty of charlatans out there, claiming that skill too, who work in bicycle shops. Really though, you'd just have to mount and test ride the bike in order to properly assess the comfort level, fit, and performance of the bike for yourself. Try to select a bicycle shop that has competent employees, who can better advise you concerning "fit". In most cases, the correct "fit" can be dialed in if you're anywhere close to the proper bicycle size.
Sometimes, finding a bicycle shop capable of a "proper" fitting, can amount to nothing less than a crap shoot.
Whenever it comes down to frame materials, the touring material of choice has always been steel! Though carbon is intensely strong, steel remains the touring leader. I can't recall a touring bike ever made with a carbon frame or fork. To my recollection, it's always been steel. I know that I've heard of more carbon fork recalls than I have of chromoy steel forks being recalled.
I know one thing for certain. If I ever purchased a CX bike with a carbon fiber fork, I most certainly would NOT be changing it to steel. I would simply use it for its intended purpose and that's it!
Your frame material for most types of bikes, is a simple matter of choice. However, when it comes to a touring bike, there's not much choice. It's either going to be steel or aluminum, and there's much more available in steel than aluminum when considering touring.
Choice is a great thing! It's a prime mover in the arena of freedom. Our taste buds, likes, dislikes, and whims, all rule within this arena. That's the way it is when considering brifters and bar end shifters too!
