Just buy either, you will eventually own both, out of curiosity. See which one you like better. I prefer the Gillette Fat Boy, or Gillette Slim Adjustable.
I started nearly two years ago with an Edwin Jagger DE89 and now have nearly 10 razors, more vintage than modern. If I were to start all over again with the knowledge I have, I would get either a RazoRock DE89 clone with stainless handle ($20 I believe) or a Gillette Slim adjustable if you want vintage. Lots of members say the vintage Gillette tech is a good start. It is indeed inexpensive, well built, but I find mine quite aggressive and a bit rough for my tough beard. Sent from my iPhone using Tapatalk
Id go with a fixed. That way, youre focusing on your technique and arent getting bogged down by trying different settings on the razor. Later, if you want to try an adjustable, you always can.