Vanilla Vs Realism Whats the Difference?

whats the difference then? I assume im playing the vanilla version. Im well into my first campaign and have found most of my battles quite easy(I thought this was because I always make sure theres a lot more us than them). Im playing on the medium setting(well it is my first go) and the AI does seem a little predictable. There have been some exceptions to this when I've been absolutely snotted by the AI and left wondering what day it is. Is this because Im so incompetent that the Ai thinks im a genius or should I play the realistic version or would the harder setting on vanilla give me more of a challenge. Dont get me wrong im enjoying my current campaign and still have a lot to learn( I haven't seen the dreaded elephants yet and have only skirmished against one chariot unit in a battle that turned out to be a bit of a none event because the seiging army attacked my city without any equipment/artilleryand ran off when I came out to meet them). Im just wondering about what level to play my next game at?

There is such a thing as an arcade mode to R:TW, but I assume you are not reffering to that. It is turned off by default and gives unlimited ammo, no fatigue and near-unbreakable morale to all units. Most likely you have heard of the Rome: Total Realism modification for R:TW 1.2. It makes the game harder, more realistic (realitively speaking) and more fun. There are several other good mods out there too: have a look at for example SPQR and Darthmod. My personal favourite is Europa Barbarorum (exquisite historical detail and probably the most challenging mod around) but still in beta phase. You can view of them on the hosted mod forums of the Total War center. Keep in mind though, that these mods are made for R:TW 1.2 and come with the limitations of this version: unchallenging A.I. (even worse than in 1.5) and problems with the cavalry charge.