Is upgrading ships worth it? Pretty newbie here and it seems that upgrading ships is as expensive as building new ones. Maybe I'm missing something here.
It really depends on what you want to do with the ships. If they're transports and you never expect them to see combat, it's probably not worth upgrading. The old transports serve exactly the same purpose, as they have the same speed and same cargo capacity.
If you use your ships for war and naval combat, newer ships will always beat older ships as their hull and cannon values improve with each version. For the exact values refer to
the wiki. This has recently become more pressing with the addition of engagement width. An outdated heavy will occupy the same space as a brand new one would, which will make your navy a lot weaker against enemies with current ships.
If you use them to protect trade, there are diminishing returns to keeping old fleets around as newer ships give significantly more trade power (on the rough order of +25% per upgrade).
Upgrading indeed costs the same as building new, but that also means older and newer ships have the same maintenance. For a one-off cost you get more bang for the same monthly buck if you upgrade.
It preserves the sailors, your fleet organisation, your naval force limit and is much quicker as you can bulk-upgrade large fleets and repair them to full strength all at once in a single port in 8/10 months (dock/no dock). Building a new fleet takes years and dozens of provinces.
If you have the force limit, sailors, provinces, time and maintenance to spare, adding new ships is indeed better. If not, consider upgrading.
