Two URLs on different domains: one is homepage and another one is inside. Both have PR7. If I'll buy link on homepage is it going to be more valuable for my G. SERP than link on inner page?
It all depends on which page people link to more. If there are more incoming links going to the main page, your link located there will be 'worth' more.
If you want a backlink to help you in SERPS then the site where your link will appear must be related to your site plus it have your link with an anchor text that your trying to optimize in SERPS
even if someone rats you out google won't target you specifically, they use the reports to improve the algo I still want to know how google is going to differenciate paid links, text link ads has a footprint and can be easily tracked but most of them can't
I do not think that it matters, although if an inside page has gained PR7 I would go for that as it might well climb higher, I am assuming the index for this site is higher than a PR7. Does one page have more relevent text to your site than the other, if it does choose that one. What page has fewest outgoing links from it - choose that one.
Homepages generally have more exposure, i would go with the page that has most relevance to your site.
i think it depents on the outgoing link number. pages with low outgoing link number will help you more
Whichever site is more relevant to yours and you need to make sure that it doesn't look like a paid link.
1st option: go with the page that is more themed to your site (similar content) as # of links alone is not worth much 2nd option: If both pages are similarly themed (or not the same theme as your page) go with the page that has the least amount of external links. The less outbound links a page has the more PR is passed to your page.