From the Wiki:
Jominian Attitude
Inf, Cav, Dra: MaxMorale +20%
Inf, Cav, Dra: Supply consumption +2%, +6%, +4%
Clausewitzian Theory
Inf, Cav, Dra: MaxOrg +5%
Inf, Cav, Dra: Supply consumption +2%, +6%, +4%
I don't believe the effects have been altered since the Techtionary was written, but I don't feel like delving into the game files right now. Too old and lazy.
But, from there, the effects of other Army inventions are altered depending on which one you have initially chosen. For example, Telegraph Coordination:
If you are Clausewitzian, it effects:
Inf, Cav, Dra: MaxOrg +2%
Inf, Cav, Dra: Supply consumption +2%, +6%, +4%
But if you are Jominian, then it effects:
Inf, Cav, Dra: MaxOrg +1%
Inf, Cav, Dra: Supply consumption +2%, +6%, +4%
and so forth with other Army inventions as well. Jominian gives you greater initial increase in Morale, but then subsequent inventions will cause you to continue to fall behind in Organization in relation to Clausewitzian Theory. The occasional invention will help to increase your morale more vs. Clausewitzian.
Organization and Morale are defined in Victoria in this way:
Organization
This represents the efficiency of the unit’s use in battle, as well as how fast its morale regenerates. Note that, unlike in previous patches, 1.03 has removed the bonus to province occupation time for high organization armies. Instead, there is now a bonus given to armies which share the same culture as the province they are occupying.
Morale
This determines how resolute the troops are. This is important because a unit’s morale decreases as a battle drags on, and if it runs out of morale it will retreat, even if it has not yet been destroyed.
So, initially the Jominian nation has an excellent edge over those nations who chose Clauswitzian, especially if they go calvary heavy in their force compositions, since they can force the Clauswitzian armies to retreat fairly easily. Later in the game, however, the increased Org of the Clauswitzian armies, along with the increase firepower of infantry, allows them to regain their Morale much quicker than the Jominian armies as well as become more efficient at killing enemy troops. In the late game, Jominian armies suffer horribly against their Clauswitzian contemporaries, assuming all else to be equal.
Which is essentially exactly what el_slapper said, except I killed a whole lot more electrons in saying it.
