Narratives aside (and very good ones may I say!) allow me to reiterate a few points and pose some new ones, rather than counter the host of arguments that have been made in my absence:
One's connection to the Light Side of the Force is negatively affected by war, take the Jedi Code:
There is no emotion, there is peace.
- war creates anger, hatred, pain etc. and it dispels peace.
There is no ignorance, there is knowledge.
- war destroys knowledge, both through killing those who possess it and destroying records that hold it e.g. the destruction of the Jedi Temple, and the Jedi Library on Ossus.
There is no passion, there is serenity.
- war encourages passion, in the heat of battle it is all to easy to embrace ones emotions and allow them to unbalance you, this is what happened to Anakin Skywalker.
There is no chaos, there is harmony
- war creates chaos and death and causes rifts to open up both physically and spiritually. It is often difficult to achieve harmony and serenity in the midst of battle.
There is no death, there is the Force
- this line is not exactly relevant, but nonetheless seeing countless die before you, seeing their lives wasted may make a Jedi doubt the integrity of this line.
All together war is the antithesis of what a Jedi stands for and oppossed to the Light Side of the Force - as such when a Jedi engages in war they risk losing affinity with the light and becoming unfocused and unbalanced.
What is important though is to see the connection between the Force and lightsaber combat, the Force is an intrinsic component of the lightsaber, you cannot simply say they are entirely different realms. As Wookieepedia says, it is impossible to achieve true mastery over the lightsaber if you lack a strong connection to the Force. And the lightsaber forms themselves rely on strength in the Force e.g. Ataru and Form V. Dun moch is also evidence of this, it was often used by the Sith to unbalance their Jedi opponents by encouraging them to embrace their emotions. Darth Maul uses this against Obi-Wan Kenobi if you recall:
"Your rage has unbalanced you. That is not the Jedi way, is it?"
Imagine the effect that a prolonged war would have on a Jedi's affinity with the light, a powerful master such as Satele may be able to maintain serenity, but the same cannot be said for the less experienced of the Order. Lets also consider that it is through meditation and serenity that one draws closer, and therefore more powerful, in the Force. The PT Jedi Order experienced 2000 years of peace, in which they could bring themselves closer and closer to the Force and become more powerful because of it. As such they can augment their prowess with the lightsaber with their strength in the Force. Meanwhile those Jedi who have only experienced war will become weakened because of it. The crux of this argument is that war weakens Jedi and peace strengthens them. Indeed if anyone has played the Sith Warrior storyline they will recall the Jedi Master on Hoth who had spent many years in solitude, drawing closer and closer to the Force, without the chaos of battle surrounding him he grew more powerful:
"The Force is with me, greater than ever now. I suspect I could defeat you quite handily. But I'm no longer concerned with the tidings of this galaxy, or these times. I only seek to continue my transcendence."
We also cannot disregard the effect war has on teachings. Ventessel brings up 'rotations' etc. to deal with such problems, but he does not take into account a major factor: death. War takes countless lives, many of which would have been Jedi Knights skilled with the lightsaber, how can a Jedi train new padawans if they are dead? During the Great Sith War many of the Order's most skilled duelists were killed or indisposed e.g. Ulic Qel Droma, Exar Kun, Cay Qel-Droma, Vodo-Siosk Baas and many others. And lets not forget the loss of the Great Jedi Library on Ossus, at least half on the Jedi teachings were destroyed, many of which likely encompassed lightsaber combat. Then we have the Mandalorian Wars, a huge portion of the Jedi broke away from the Order, likely many of them were Jedi Guardians and Sentinels. All were lost during the Mandalorian Wars, they either died or fell to the dark side and were later killed in the Jedi Civil War. During that period the Dantooine Jedi Enclave was razed, more teachings lost. And then we have the Great Galactic War which saw the destruction of the Jedi Temple, and the loss of countless Jedi Knights. During the Cold War Jun Seros, Jaric Kaedan and Orgus Din were all killed, and that was just during the Cold War - can you imagine the loss of powerful Jedi Knights during the war itself?
All this accumulated with the next generation of Jedi being completely without substantial teaching in the Force and in lightsaber combat, so all that combat experience built up in periods of war was lost and never utilized. Do you recall Mical? When he came of age their were no Jedi left to train him, think how many other potential Jedi would have been lost and how many Jedi would have be incompetently trained by the few Consulars and Historians that remained. War has a tendency to seriously damage the population of skilled lightsaber duelists, making the next generation comparatively weak. Whereas in a period of sustained peace, this is not a problem. Knowledge is gained, retained and passed on.
Finally we are giving too much value to first hand combat experience, yes it is important but once that experience is retained it doesn't have to be lost, it can be preserved and passed down to generations to come. Take the lightsaber forms, they flourished in a period of war were Jedi could test themselves and learn from experience. But once these forms were lain down and preserved, there was no longer any need for combat experience. Because that experience can essentially be attained simply by learning a form. A Jedi can learn how to deflect blaster bolts, not by engaging in war, but by learning Soresu. A Jedi can learn how to fight a lightsaber wielding opponent by learning Makashi. Take Dooku, he had never and never has fought in a war, and yet he is immensely skilled with the lightsaber and has defeated many lightsaber wielding opponents.
So in that sense the PT Jedi Order has just as much 'combat experience' as the OR Jedi Order did, they have all the benefits of war experience and none of the negatives. The fact that many if not most Jedi survived the Clone Wars is testament to this. What the PT Order has in their advantage however is a closer affinity to the Force, which does - and I cannot stress this enough - have a significant impact of lightsaber prowess, the two are inseparable. In a nutshell the PT Order is all the more stronger the OR Jedi Order because Jedi thrive in peace and are weakened by war - that is the way of the Force.