Hi, and welcome to the TDP Forums!


I would definitely recommend going with the EF-S 15-85mm f/3.5-5.6 IS over the EF 24-105mm f/4L IS. But, I'll try to run through the pros and cons of both lenses.


The 15-85mm is one of Canon's two excellent general purpose zooms for a crop body (the other is the EF-S 17-55mm f/2.8 IS). Of the two, I think the 17-55mm is better for indoor/outdoor use, while the 15-85mm is better if the primary use will be outdoors, as is the case for you. For indoor use, it really needs a flash - and you've already got that well covered.


The 24-105mm is a very nice lens, but not really wide enough for general purpose use on a 1.6x crop body (it starts at 38mm FF equivalent, meaning it's not really even wide angle). Optical quality of the 15-85mm vs. 24-105mm is pretty similar, so that's not a real differentiator. However, optical quality of both is much better than the kit lens, so you would likely find yourself not reaching for the 18-55mm even if you keep it, or find yourself less happy with shots between 18-24mm taken with that lens instead of the 24-105mm, if you go that route.


The 24-105mm is definitely better built than the 15-85mm (and the latter is much better built that the kit lens). One reason I initially bought the 24-105mm was for the weather-sealing. However, weather-sealing only helps with a sealed body (e.g. 7D), which the T2i is not.


I agree with Daniel that 2 years is too long to use a lens that's not ideal for your current needs. You plan to get a FF body in two years, but maybe you'll find yourself shooting mainly wildlife or sports, in which case the 7D (Mark II at that point, probably) would be a better bet. Also, if you do get a FF camera, that's the time to get the 24-105mm. It's the 'kit lens' for the 5D series, meaning when purchased with the body you're only paying $800 for the lens, instead of the nearly $1100 for the lens alone (when I got my 24-105mm, I bought it used, then when I later got the 5DII, I sold the used copy for the $800 which covered the cost of the lens with the kit).


Canon does raise their prices periodically. There was an increase in 2008, another in 2009. If you go HERE, you'll see some information on this latest <s>gouge</s> price increase. At that site, you can also click on a lens name, then scroll down, and you'll see a plot of average pricingfor that lensover the last few years.


Hope that helps, and good luck with your decision!


--John