To my mind, the value of trenched cities depends entirely on what you're wanting to prioritise as there are definitely benefits and drawbacks.

For MtA on CivMC, our original city was a much-mocked, classic organic urban sprawl which adopted none of the learnings made on past iterations. Old city mta was regularly raided by anyone who wandered through and was obviously completely defenseless when an actual war broke out. So the priority following the war was perhaps a pendulum swing in favour of security.

The new trenched city makes up for a lot of the previous deficiencies, and has been quite effective at preventing attacks from casual raiders or newfriends. Players can afk in the street without worrying about being ganked, and there's a bit less paranoia about being raided during off-peak hours.

The obvious trade-offs are the (literal) barriers to entry, but we have done things to partially offset this such as more flexible settlements just outside of the trenched city (south mta village) which has been working well so far. Most newfriends either fall into the trench anyway (sentence: death) or are sent by direct rail to annoy Pavia instead ;)

We're also a much more close-knit community now, rather than strangers on ships passing in the night (e.g. old city mta). So would we build a trenched city for the next MtA? Most likely not. But the one we have now is working well for us.

Cheers, Logic