Peter, you ask a very good question. I recently went thru the same reasoning as well. My decision was (at the time) to buy a Canon 17-40 mm L series lens for about $640. I didn't do so, but here is why. I found a good used 10-22 mm Canon EFF-S lens on the used market and bought that. Frankly, I should have stayed on plan. Because 10 - about 14 is just too wide for my tastes. I'm using a Digital Rebel XT with 1.6X crop factor. At 10 mm if you are on the overlook at a park scenic area, the angle of view will capture the railing that protects the overlook.
The optical quality on the Canon 10-22 is VERY good. No issue there. An advisor told me that this lens is highly specialized, but when you find the right situation for it, it is superb. Now, the lens I use most often is Tamron 28-75. I also have a low end 35 mmm prime that has a nice angle off view but the image quality is good, not great, as I prefer to have.
Canon also makes a L series 16-35 mm lens but the price is very high, over $1,000. Must be a good one though. I don't intend to find out for my own first-hand because the price is too high.
But, its surprising how often I shoot landscape with my 75-200 mm IS f/4 Canon L lens. The reason why I use a wide angle zoom and a moderate telephoto both is that the wide angle zoom works well on landscapes where I want mostly near-by features. The 75-200 works better when the foregroundd is less interesting than the far away scene is. The classic examples here are a meadow with butttercups (use the wide angle telephoto) and a mountain top with rugged boulders (use the 75-200 mm here).
So, to kind of summarize, you may be able to do well with either approach, wide angle zoom or telephoto zoom. The obvious solution is to get a lens with a very wide range of zooms on it. Something like 18-200 for a price of around $350 maybe. The reason why you won't see too many professionals or advanced amateurs with this approach is because the design compromises necessary to get such a wise zoom range - especially at a reasonable price, preclude very good image quality. So, my personal advice to your situation?
Pick one, wide angle zoom or medium telephoto. Use it & enjoy it. When circumstances permit, get the other end of the spectrum covered. OR (happy thought) buy both. But whatever you do, don't buuy low uality. Medium quality OK. Financial reality is not going away. But just don't buy low quality.
Tamron & Sigma do very well for medium quality with selling prices in the $350 to $600 range. The big name OEM's do very well for high quality with selling prices in the $600 to $1,100 range. This statement is going to controversial. Oh well, just my take on things.
You can see various landscapes and so on with XIF data on the focal length and in some cases with data on the specific make and model of lens I used at www.pbase.com/goodlistener
. Hope you enjoy the show.