In case of reciprocal links, we are passing some amount of PR to the site to which we are reprocating. but in case of one way link, there is no risk of any loss, we are just benefitted if we get approval from the site to which we have submitted. So try to get as many as one way links. Reciprocal links are helpful if the site with which you are reciprocating is of high PR. Since you get a lot of traffic for your site from that site.
One way links are just better to have because there more legit looking and with reciprocal links you can only get so many of them until your flood your site out then it looks like a big link farm.
In one way link are getting free link juice. While in Reciprocal link you are getting link juice from the reciprocal URL but in rewards that link from your page also get some link juice. So if you are getting one link having PR 2. will help your site. But if you are reciprocating with PR 2 page and in rewards you need to reciprocate that link on PR 2 page will not make any benefit for your website.
Always go with 1 way links if you have a choice. One way links are always better. If you have to have a reciprocal link then make sure the other site has a higher page rank, and is relevant to you site.
Well....relevant One-way or natural links are always most valuable links and obviously have lot more value than reciprocals.....but its hard to define how much more valuable they are........as in one way links there also some are high quality and lw quality and i think it will not wron to say that a lower quality releavnt ine way link is also more valuable than high quality reciprocal link..........