Hmm, I'm not sure I understand:
So as an ENWorld supporter I get the 3E and 3E version for 3$/month, i.e. 36$ total.
As an RPGNow subscriber I get only the 4E version for 50$ total.
Now, what's the advantage for the RPGNow subscriber again?
Here it's not per month, so it's not $36. it'll take over 2 years here. So it's $72. In addition, it's behind the rpgnow subscriber releases by 6 months.
Whether that's an advantage to you or not is something nobody but you can decide. As I said, I'm willing to convert an rpgnow sub over to an EN World one of the same value ($49 or 14 months or whatever 49/3 is). If you think that's a better deal, convert it over. If you think the rpgnow deal is better, stuck with it. I don't mind which you choose - I'm not trying to persuade you towards one or the other.