I'm not sure what you mean... if I understood correctly you mean blogroll links vs comment author links. Well, in that case, of course blogroll links are better because they are sitewide which means many more backlinks and probably more direct visitors.
Ah yeah I see now... Blogpost links are more valuable because posts appear also in archives/categories ect... so you will get 3 or 4 backlinks for each link in a post...
Post links are always better becz many a times the post page has some PR attached to it which will help you get the PR juice but more often than not the comment page has very little PR so i would stick with the blog post however blog comments are easy to get and you can have many blog comments and sometimes some very good PR if you are a good commenter and many sites reward there regular commenter with a permanent link too that is beneficial too so choose the one that suits you Cheers Abhishek