If you are only going to run oil in one engine a two tank system is not a bad way to go. Making biodiesel does add another layer of complexity, adds some cost, and creates a glycerin waste product that you will have to deal with one way or another. You will have a lot more options for using biodiesel.

We started out blending 30% veggie oil with diesel for a few years and never had a problem. But after reading about injector and ring coking that can happen with veggie oil we started making biodiesel. My nephew still run 100% veggie oil in a Detroit 6-71 on an irrigation pump sometimes.

If you set up a two tank system you could have the best of both worlds. You could run veggie oil, or B-100 all year and not have cold weather gelling problems.