• Where in the comparison tables do I find the sensor size comparison?
There are essentially 4 different sizes. APS-C being the most common, and being 1.5 times smaller than a full frame 35mm sensor (with Canon's APS-C, its 1.6). There is also APS-H, a rare size - only one I can think of is the Canon EOS 1D Mark II N, its 1.3 times smaller than a 35mm full frame. Theres also the 4:3 sensor, which is a bit different since its aspect ratio changes as well as its size - but it is 2 times smaller than a 35mm sensor. Then of course, the 35mm sensor is 24mm x 36mm.

We'd all love to have full frame 35mm sensors in our camera, but that requires a much more costy investment, you'll need $3k for body only, then you'll need to spend more on lens that can match your sensor. Lens perform much better on APS sensors, because the refracted image onto an APS sensor is brought through the lens sweet spot, so mid-range lens act more like high range lens on APS sensors. Lens problems can often be irrelevant on an APS sensor (vignetting, corner resolution, etc), while they become serious problems on a full frame sensor. Expect to spend a lot more on lens for full frame than for APS.

I digress, sensor size does make a difference, but all sensor sizes have manufacturers that do really well with them.