I followed this guide and, I am about one day from the end of Beginners Protection and I suddenly realized something.
After going through the guide again, there are NO build orders for the City Wall. It is mentioned ONCE and, never again. Now, I am 30 hours from 'no umbrella' and I am now trying to get my wall above 10 before I get exposed. My fault for not reading the build set a couple of times but, damn. A wall is kind of important.
Welcome Noel. Well the subject you bring up is not cut and dry, and it will indeed lead to several different answers pending on who you talk to and the building style of the city. And more importantly if you play Conquest or Revolt worlds.. etc...
In a nut shell, some swear by a wall (level 25 and tower) at all times no matter what. On other hands, you got some that never build walls and towers. And then you got some that do either pending on the build style of their city.
So don't get to caught up in one way of thinking.
Reasons ? (way too much to type, but..) I will strictly speak from a Conquest world point of view now:
A wall and tower also will help a enemy hold a siege on you if they do land a CS in your city. As you try to break their siege the wall level and tower of your own city is defending them and helping keeping you out.
At the same time pending on the city/troop build, a wall could prevent the siege in the first place.
50/50 brother. Not cut and dry.
IE: If you have only offense in your city, and you nor anyone else can get to your city with DLU in time, your only hope is to dodge the offense right before the CS lands and cancel the movement so they return to the city seconds after the CS lands... They then attack the CS party and hopefully break the siege for you. This works BEST if you have no wall or tower as you will take more of their troops out. The trick here is to actually let the CS land and "snipe" it on the backend. No wall, no tower is best for this.
In reverse, if you could get DLU there in time, or the city was a DLU city anyway, then a wall and tower is best to help prevent the siege as you will snipe on the front end (before the CS lands).
Hope this helps.