An interesting question.

In most of the really "up scale" mods -- XGM, EB, et. al -- the walls come with progressively higher levels of Law and Happiness scores reflecting public and commercial sense of security. This would have been good for Vanilla as well, IMO.

In Vanilla:

Palisades are useful only for buying you one turn -- no immediate break-throughs unless expensive elephants or slow artillery are brought to play. That's about it. Towers are few and usually ill-placed. Still, a competent defender in SP (In MP I assume rams have support teams) can sally during an assault and steal the rams from the attacker, winning a quick victory. Thus, a smaller force can defend for much longer against a bigger one -- unless they build 5-6 rams, in which case you're dying in the square.

Wooden Walls are an abhorrent waste. There is, in practice, so little time difference between breaking a wooden wall and a palisade that it adds nothing and the restriction of cross wall missile fire goes both ways, since (of course) the wall is erected without a fighting platform or firing loops. Bottom line, keep an eye on your population, only build the stupid wooden wall in the last two turns before you become eligible for the next tier government building -- so that you can get a stone wall as soon as desired. If you're in a backwater, don't bother -- a palisade is all you'll ever need against 98% of all rebels and brigands.

Stone Walls bring the first new defensive strategies. Fighting on the walls is often the best choice for sword troops and javelins from above hammer home without shield unless the target is "turtling." Shooters on walls take far fewer casualties and can missile duel at great advantage. Towers are better placed, though silly blind spots are still too frequent. Once you know you cannot hold the walls, it is often possible to stall the attack and still set up your street/square defense after attritting the attackers to good effect. Above comments about garrisons are apt, however. A small garrison must sally during the assault and take siege towers/ladders out for a quick win (rams burn 97% of the time "on their own" it seems), otherwise, they get killed by multiple break-ins etc. The instant tower conversion is patently silly and a gross advantage for the attacker.

Large Stone Walls have towers that hit much harder and ladders cannot be used against them, requiring siege towers -- and taller ones -- or mining for the attacker. The siege towers built by the attackers mount the same firepower as the walls, so the advantage there is to the attacker, who doesn't have to go nose-to-nose with a tower as there are still blind spots. The only real advantage here is time. It takes significantly longer to undermine, knock down or climb a tower tall enough to deal with these walls, and ladders are the only "fast" way up.

Epic Stone Walls have towers that hit just as hard and fire even faster -- but so do their siege tower opponents. But the city KEEPS ITS SAME BLIND SPOTS DESPITE 3 or 4 iterations of walls built acrosse 7+ game years! Epic Gatehouses have slightly better fields of fire, but that's about it for differences. Usually not worth the cost or time -- since your probably only a couple of provinces away from winning by the time you can build one of these anyway.


Thoughts:

Walls, for SP players who've disabled or grossly extended the battle time limit, are not much of an obstacle. One turn of construction and you're probably killing more defenders with "turned" towers than the AI kills with the long-range shots it gets before you're safely snuggled in a blind spot. With a 45 minute or less timer on, however, Large and Epic walls are much more of a defense as any kind of "finesse" in siege tower placement etc. can cost lots of those minutes and leave you without time to get to, climb up, climb down, get to square, kill general and last pike unit. This forces a more "frontal" strategy where the AI actually gets to attrit you a bit -- more challenging.


Things I'd like to see:

Towers all ballista equipped with mini arrow-firing "turrets" between. If they're supposed to represent garrison firepower, then let's have a goodly volume of fire.

Fewer blind spots -- maybe one or rarely two in a whole wall, not the 3-5 typical now. Even one or two town plans without a blind spot at all.

Cities NOT all built on flat level spaces, but nestled on hills etc. Masada would not have held out as it did had it been built on a Gaza beach. How about a semi-circle where the long "wall" is actually the water.

Firing platforms to put artillery up on walls. As it is, I have to hammer the crap out of my own walls to lob bombs at enemy towers.

Ladders getting pushed away -- at least once in a while -- by defending troops.

A breach that looks like a breach instead of a neat cut-through doorway.

Captured towers that stop firing -- for anybody -- once captured by the assault team.

Cities going to the ally who takes and holds the square for 3 minutes and NOT just whoever initiated the assault (not that I havent' used an ally's full-stack to bleed for my 3-card stack's right to own the city ).


Rant concluded.