Originally Posted by
shipwreck
A bike shop would consider it a faster job to pull the cassette. You pull the crank and its a little more involved, the shop charges more. And really, after fifty or so miles the crank should be checked for proper torque again, particularly with a heavier rider. The cassette would be a set and forget issue. Other than the very good point that a slightly longer chain might be needed, it is less involved.
Personaly doing all my own work, I own the tools to do either myself. I would consider a cassette change faster and easier.
To the OP. Its really simple. Don't read any of this debate on your thread. If you change one or the other, or both, thats going to depend on what recources you have available to you, what they have at any shop you might have your work done at. cplager does have a point that one smaller ring will cost less than a whole cassette, see what they will charge you to change it compared to the cassette and possibly a chain.
After you become a seasoned tourer, you will enter the next step of cycling, which is constantly disagreeing on the details of every aspect of the hobby, from equipment, clothing, hygene, food, and whether you should crack your soft boiled egg from the big end or the little end. Its just as fun as actual touring when your not actualy touring.
O.k. I can buy your explanation (although I'd still rather change a chain ring personally).
The only other thing as far as hardware goes that I'd like to remind the OP is that if you do change cassette but keep an 8 speed, you'll be making the jumps between the gears wider. Some people don't mind that at all. I find my 8 speed 11-32T too wide as it is.
+1 on ignoring all of this and getting out there and riding. After a few day trips, you'll see what you like, what you don't and then you'll have a better idea what to do next.