Re: vanilla vs. mods
For a long time I was a big fan of XL. The attraction for me was the larger number of factions which allows more variety and role play. However, I got tired of it because it has certain drawbacks. For one thing, it has even more units than the original or VI, which means more opportunities for the AI to mess up and (for example) train an army that is mostly javelin units and is easily wiped out by a better designed army. (The Hungarians tend to do this.) Also, XL increases farm income across the board. This is supposed to favor the AI which farms much better than it trades. However, it also makes the rich provines even richer, which favors the player, who can target wealthy provinces more intelligently than the AI does. So it really depends on what you are looking for. You get more variety but sometimes you get less challenge. I never tried the Tyberius patch. Maybe it corrects the problems?
I also enjoyed Samurai Warlords. I think it increased the challenge because the unit roster is smaller, and has fewer useless or overpowered units in it, so the AI has fewer opportunites to make recruitment mistakes. Also, the starting positions can make things really challenging, depending on who you play. I suggest you use the gnome editor to eliminate the crossbow unit (the AI builds too many and suffers for it) and also eliminate the kensai unit, or at least tone it down. Its too powerful. I think the most recent version may have taken care of the crossbow and kensai, but I'm not sure. The strengths and weaknesses of this mod are opposite to XL. You get less variety but more efficient opponents.
In those simple times there was a great wonder and mystery in life. Man walked in fear and solemnity, with Heaven very close above his head, and Hell below his very feet. God's visible hand was everywhere, in the rainbow and the comet, in the thunder and the wind. The Devil too raged openly upon the earth; he skulked behind the hedge-rows in the gloaming; he laughed loudly in the night-time; he clawed the dying sinner, pounced on the unbaptized babe, and twisted the limbs of the epileptic. A foul fiend slunk ever by a man's side and whispered villainies in his ear, while above him there hovered an angel of grace . . .
Arthur Conan Doyle