I feel like you have very different questions here.
To answer your first question:
is some research in regards to how font-weight affects readability?
Yes, there is. First you have to understand that type/fonts are judged by their "readability" (how easily can words, sentences, and paragraphs be read by an average reader) and their "legibility" (how easily can letter forms be distinguished from one another).
Studies have shown that readability tends to increase when using a "normal" or "regular" font weight (i.e. 400). The reason for this is that it when words and sentences are able to read quickly the reader's eyes will actually slow down their normal blinking rate, which allows the user to not grow weary reading over long periods of time. Yet when lighter or heavier weights are used in large blocks of text, readers tend to blink more because they have to concentrate more while reading. Lighter type weights introduce more negative space and heavier type weights introduce more positive space. Both require readers to concentrate more.
For headlines, your goal should be readability but also legibility. Studies have shown that typefaces with higher x-heights are more legible.
To answer your second question:
So here is the fiddle that I'm working on http://jsfiddle.net/T7b6E/
I personally prefer the title with font-weight:100 (more slick, modern etc.)
The first thing to remember is that simply using
font-weight: 100; in HTML doesn't actually create a lighter typeface. The weight has to be in the font. Most standard fonts out there, come in 2 weights (4 styles): Regular, Italic, Bold, and Bold Italic. In HTML that's
font-weight: 400 and
font-weight: 700. If the font that you're trying to apply a different font-weight to doesn't have that weight, the browser is going to try and approximate what it could look like. And it could get it wrong. And depending on the operating systems and even browsers, it could look pretty different.
There are so many great web-type foundry services out there today who are providing type in multiple weights, I would investigate that.
The general rule of thumb I use with type weights are, the larger and shorter the type (i.e. headlines), the easier it is to use lighter weights. The longer and smaller the type, you're better off using regular weights and utilizing heavier weights for emphasis. This approach also falls in line with studies that shows people don't read, they scan copy online.