What questions should a player ask himself when deciding weather to play english or d4?

-.- okay 1. im a positional player so i wanna go away from e4. and i dont know which i prefer. i dont know the ideas behind each

Then you're not a positional player.  Stick with 1.e4.

Try Nf3 and get the best of both worlds!

I know the ideas behind d4 just not c4. sorry for the miswording -.-

Best of both worlds? how?