Personally I prefer Telluride because it's still has more of the smaller mountain town feel. You'll get more for your money in Telluride. Aspen has much more glitz and glamor to put it nicely. I personally prefer the skiing and snowboarding in Telluride over Aspen as well. But on the other hand, when dealing with investment properties, I'd think Aspen would be the better of the two. I guess it kind of depends on how nice of a place you're looking to buy, whether you're planning on doing a Vacation Rental of it or if you plan on getting a 6month or year lease from a local.
Based on your post I'd assume you're thinking that you're thinking of going with a vacation rental as opposed to a 6 month rental. Which in that case, I'd think Aspen would probably give you more opportunities to rent it.
I'd probably jump on
VRBO® is Vacation Rentals By Owner and look up what other vacation rentals are renting for in the area. Then assume the VR management company will be taking anywhere from 40-60% of that for management costs and that it will probably be rented a lot in late November through mid January and then in March... Then compare the prices between the two areas to actually buy it and see which would give you the best return on investment. Telluride has a good chance of one day exploding in price (but that might take 30+ years) where Aspen you can pretty much know exactly what your rate of return will end up being.
Hope some of that helps.