I don't think running 6 days a week will make you faster unless of course some of those days are interval training, speed work, hill repeats, etc. Plans that include this type of activity are generally for more advanced runners.
Not true. Running more often, in Heart Rate Zone 1 or Zone 2 (which is very easy), will make you faster. Especially for the beginner or moderate beginner.
Yes, you are correct, once you get more advance you will need to add speed work to get faster, but that's not where most people on these forums are.
For most people, like the Original Poster, running more often and running easy will make you faster. You will continually be able to run at a faster pace while keeping your Heart Rate in the same "relaxed" state.
As I mentioned previously, the Hal Higdon Dopey plan had 2 consecutive days off from running every week. I followed it religiously and was able to complete my first marathon in under 4 hours (while running a 5k, 10k, and half in the preceeding days). I really don't think that 6 days of running would have had any benefit on my time for the marathon, other than possibly making it worse because I was worn out from running so much during training.
Congrats! I've never said that other plans won't get the job done. They absolutely can.
I agree with the previous poster that running 6 days a week will make you fitter unless you get injured, which is likely for a beginner marathon runner. Most beginner runners that are looking for a plan to use for the Marathon, Goofy, or Dopey will get burned out and overtrain if they run 6 days a week. Most advanced runners that can run 6 days a week probably have their own plan of attack already. I certainly wouldn't recommend running 6 days a week to a runner seeking advice for their first marathon, Goofy, or Dopey.
It's like everyone is criticizing, without reading what I'm writing. It's blowing my mind.
RUN SLOW. RUN EASY. If you are running easy, on 3-5 of your 6 days, you won't be burned out and need an off day. Many, many runners feel like they only can run 3 days a week, so they have to push it. They run to hard, and kill their recovery. If you can't carry on a conversation while you are running, you are training to fast (unless you are advanced and doing Tempo or Threshold speed work).
I'm not saying run 5 miles a day M-F and then a long run on the weekend. Do 3 short recovery runs a week, 2 medium runs per week, and 1 long run. 3/2/1. Run easy, run consistently, run often.