Hi all, A site have subpages A1,A2...., then B add a link to A, link to A (homepage) or link to one subpage (link: A1), Which type of link is better? Thanks.
Which ever has the higher PR (or inbound links) which is likely to be your homepage or "A" unless you've really played around with the robot.txt file for some reason
You should get links to home page as well as internal pages (subpages as you call them). If you get 1000s of links to homepage and none to internal pages it's not natural.
jitendraag is right. It MUST look natural. In the real world, a site will get links to lots of its pages (unless it's a 1 page site!). While generally a link from a higher PR page is best, it isn't that simple. For example, if the link is from a lower pr page, but the content on that page is more 'relevant; to what your site is about... or perhaps if the subpage actually has lots more traffic than the higher pr page, you'll get actual visitors, not just pr passed.
Which page is most relevant for B? If A it is, than A will get maximum of value. If not, link to A1 - automatically A will get some link juice too.
It's best to focus on linking to both the main site as well as internal/sitewide pages for best results.