I can't say it is significantly worse. The thing I disliked most about Alex.exe is that the governers live way too long. There is a way to fix that though, I just never bothered. I only played 2 campaigns and noticed real improvements in battles and naval invasions.

Only once did I ever encounter a serious (4 full stacks in 3 turns) naval invasion in RTW.exe.

I have played all 3 engines and all 3 will have occasional AI sieges where they are completely outnumbered. If you auto_win it is a minor victory, if you play the battle it is a waist of 10 min as they always run away.

I have been using BI and am quite happy with it. I thought retraining would make things unrealistic, but retrained armies lose some experience. Also, aor reduces retraining.