I'm looking for a relay to provide electrical isolation?

I'm looking for an (electromechanical) relay to provide electrical isolation between two low voltage circuits (5V and 7.2V) as an alternative to using an opto isolator. I am actually looking ot compare the two on things like cost and size, but I'm not exactly sure which sort of relay to use. Any ideas anyone?I'm looking for a relay to provide electrical isolation?
You could use a reed relay (for instance stock code JH12N from Maplin) which costs 拢1.31. However, I would myself prefer an opto-isolator (Maplin stock code RA57M, cost 57p), as it is smaller, faster, has no moving parts and is cheaper. You can also get dual and quad opto-isolators if you need them.