Best AI, please.

[paleologos]

So, generally speaking BI is somewhat smarter than Alx?
In the big picture is it the most challenging?

[Zarax]

I wouldn't call it smarter, it just has bias on different functions.

[paleologos]

Does BI get to be more challenging?

[Ludens]

Does BI get to be more challenging?

Yes, but not always in a good way. As I wrote, the A.I. can do strong naval invasions, but they will also start wars by making stupid, undermanned attacks, like the Romani on Corinth in my campaigns. Since we had no land borders and the Romani weren't in a position to hold Corinth, the war was over as soon as I wiped out their petty forces, and the attack was essentially pointless. However, it did mean I had to patch up relations or lose a trade-partner, and a few dozen turns down the line they would try it again. For me, that's frustrating rather than challenging.

I am sorry that I can't give you a clear yes or no: it depends on your tolerance for such things. I switched back to vanilla R:TW. I imagine, though, that when playing a faction that would require naval invasions (Carthage and Rome for the Punic wars, Casse and nearby factions), BI could be an improvement. I maintain, though, that there is no other difference between the A.I. of R:TW and BI.

[Mediolanicus]

Yes, but not always in a good way. As I wrote, the A.I. can do strong naval invasions, but they will also start wars by making stupid, undermanned attacks, like the Romani on Corinth in my campaigns. Since we had no land borders and the Romani weren't in a position to hold Corinth, the war was over as soon as I wiped out their petty forces, and the attack was essentially pointless. However, it did mean I had to patch up relations or lose a trade-partner, and a few dozen turns down the line they would try it again. For me, that's frustrating rather than challenging.

I am sorry that I can't give you a clear yes or no: it depends on your tolerance for such things. I switched back to vanilla R:TW. I imagine, though, that when playing a faction that would require naval invasions (Carthage and Rome for the Punic wars, Casse and nearby factions), BI could be an improvement. I maintain, though, that there is no other difference between the A.I. of R:TW and BI.

I play mostly play with M campaign difficulty and with BI. All I got are fullstacks of factions I'm at war with on my coasts.

I did play some campaign on H or VH and even my allies constantly shipped over 2-3 unit stacks...

[paleologos]

I play mostly play with M campaign difficulty and with BI. All I got are fullstacks of factions I'm at war with on my coasts.

I did play some campaign on H or VH and even my allies constantly shipped over 2-3 unit stacks...

I suspect that a higher campaign difficulty level does something to the default "personality" of AI factions. You know, transforming a "comfortable Napoleon" into an "unpatient Hitler" or something. I don't know how to confirm or disconfirm this.
I wonder what the more experienced programmers/scripters would have to say about this, perhaps conjure up a solution.

[Ludens]

It's possible. Personally, I think it has something to do with auto-deteriorating relations. A CA programmer mentioned that in M2:TW the relations between an A.I. faction and the player automatically deteriorate over time, and that this goes faster at higher difficulty levels. So unless positive interactions take place, the A.I. will eventually hate the player. I think the same applies to R:TW, and it would explain why I didn't see any differences between diplomacy at H and VH difficulty. I always pay neighbouring factions a small, regular tribute, so the deterioration does not occur. Not everyone has reported success with my method, however (and the diplomatic A.I. remains stupid).

This is, BTW, not an area of the game-engine that is accessible to modders, so I am afraid there won't be any solution.