What is better for SERP a PR 5 link from a 100% relevant site or a PR link from a 100% relevant blogg. WHat if I have a 100 % relevant site and add a blogg what happens then, better or worse?
PR 5 link will be better for the SERPs. Reason, the link will be around longer to be counted by Google. Blog content has a short life and usually has to many links on it.
Content will be 100 % relevant, what if I had a site and later added a blogg? So both in other words?
Your links to both PR5 with 100% relevance should be all the same, even if it is link with a site or with a blog as long as they are having PR5 and 100% relevance it should not make any difference for SE.
you will be wrong on both way. Reason ? ah,, why you giving a option for your niche site either you know both will do effectively work for google algo. he measure all things and you aren't going anything wrong if you doing both thing for your website.
If the targeting website you are saying or blog is related to your niche, then its better to go with any of them. You should concentrate on collecting contextual links rather then direct links. Since Google loves, them and thinks its more natural then those spammy links(which Google thinks)