M_Boats: Varnish or oil?

Hi all, I took off most of the wood on my Monty 15 and am currently sanding it all down to get ready to make look good again. I am debating whether to do varnish or oil, does anyone have any suggestions or thoughts on the matter? I would greatly appreciate some input. Also, my companion way boards are in disrepair and I am going to just make new ones. Are the monty's only set up to have 1/4" companion way boards or would 1/2" work? Thanks in advance for the help! -Ted