Hi, graduate student in biology here.
I teched for 3 years after undergrad, and enjoyed it. I also decided that I wasn't interested in being a permanent tech, that I wanted more freedom, more responsibility, and possibly, more money. I highly recommend teching before deciding whether or not you want to join a graduate program.
Insofar as what is more valuable, the PhD or the Masters, you should figure out what you want, and that should inform your decision of whether or not you go for the PhD or the Masters. I've heard that in some spheres, having a Masters provides you with a better chance to be hired than a PhD, as the PhD is expected to be paid more. As far as teaching is concerned, I'd be surprised if any decent sized or respectable institution hired a non-PhD holding teacher to teach anything but the intro level coursework.
Another thing to consider, however, is that PhD programs *do* award a Masters at some point in the trek, and will provide you with a stipend; in terms of cost, a PhD is a 5-6 year investment that will only cost you time (which is a serious consideration), whereas a Masters is a ~2 year investment that will also cost you money. Generally, choosing to leave a PhD program is frowned upon, so I wouldn't treat it as a road to a free Masters, but it certainly happens.
If you have any questions about the process of applying, or what it's like as a graduate student, I'd be happy to answer.
-I know this: if life is illusion, then I am no less an illusion, and being thus, the illusion is real to me. I live, I burn with life, I love, I slay, and am content.
-We can't go back. But I suppose we can go wherever we please.