/index.html VS. /keyword.html VS. /keyword/keyword.html

One better than the other?

[darkroom]

Hi guys,
I am working on a site with 50 different single-letter keywords. So, i hade 50 different pages for them and they appear as domain.com/keyword.html .

Now my questions are:

1. Does Google always prefer index.html pages over keyword.html pages? or index.html over domain.com/keyword/keyword.html?

If no, then under what circumstances would this be true?

If yes, then can i not make more inbound links for keyword.html(or domain.com/keyword/keyword.html) page and get google to prefer it more over the index.html?
It seems to me that google always prefers the index page and will always do since it the entering page.

2. Would it be better to purchase 50 different domains and build a 2-5 page website for each domain or should i make one quality site with 50 different pages on those keywords?