Dofollow backlink from relevant site without keyword.For example backlink from dofollow blog comment with name instead of keyword. Dofollow backlink form irrelevant site with keyword.
Good question, I see where you are going with this. I would say the site with the most authority. I say this because sites do naturally link to irrelevant sites. For example a computer modding site may link to a site on electro plating as they may be talking about chroming a computer case.
I would take both links hands down. But I would say go for the one with the either the most inbound links or the highest PR. If it was about which one to get first I would take the relevant one with the name instead of anchor first then take the non relevant one. Google knows what the from and to sites are about, the anchor is nice, but its still counts as a link.
its really hard to say and all depends on the quality of the site where you are getting a link form. if it is a really quality suite, then a backlinks without an anchor text will be very much valuable. yahoo directory, BOTW, DMOZ etc dont link to you using your keyword but ht esite name/url in most of the cases. some sites however have the keyword in the domain but not all. i would say getting links only form yahoo directory, DMOZ, and BOTW would be far more valuable than getting links with anchor text from 100 other individual directories.