Sword fighting styles are based on killing the opponent before he kills you and that's all there is to it. Saying that you used katana with "speed" and the longsword with "power" you display no less ignorance than the people you call "kiddies". You think a real feudal japan samurai wouldn't kick the enemy to throw him off balance or use his height, strength to an advantage? Or that european swordsmanship doesn't involve "speed"? Look up where rapiers originated from and try that again.
be nice. since he is a sword fighting enthusiast and actually practices sword fighting, he is primarily exposed to sword techniques that are being taught right now. And since no one mentioned chinese fencing and the european school of sword fencing was all but lost (apart from several thousand instruction manuals), the only sword fighting school left is kendo. and western fencing if you want to call foils swords.
and compared to the hollywood depictions of two-handed longswords (which almost everyone confuses with greatswords) the japanese school looks more graceful, i guess. kendo in itself is pretty stupid (you have to actually say "ey bloke, ahm gonna bash your head now" before actually doing the attack) but tournament rules generally don't translate to a battlefield.
There were dozens of different types of armor in Europe alone, of various materials and hardness(and let's not forget shields), and not everyone in middle ages was running in a full plate - quite the opposite, as a set of plate mail was extremely expensive.
Being forced to go for enemy's weak points puts you at a serious disadvantage, so if your weapon was capable of delivering injury despite enemy's armor(piercing, cutting through or simply causing enough blunt trauma) then you would definitely not try to be mr. fancypants and try and strike the weak points needlessly.
And that puts the katana at a disadvantage compared to european longsword because it's very bad at cutting through armor and mediocre at best at piercing through it.
True, but you have to consider this: The european longsword was a true weapon of war. It was effective against most types of enemies, even - within limits - against armored opponents, provided you managed to kick their feet from under them first. Europe was constantly at war with everyone, so they simply couldn't afford to carry weapons that were ineffective.
The japanese katana reached it's current form in the 17th century - a time where japan was largely pacified and no large internal battles between armored soldiers were fought anymore, meaning that the Katana almost never came into contact with metal armor.
The prime use of the Katana was as a dueling weapon against unarmored duelists. And a status symbol of the noble warrior caste, whose influence was declining steadily and sought to distinguish themselves and their nobility, which led to the secondary use of the katana - the killing of helpless peasants against which the Katana and it's extreme sharpness excelled and it's fragility didn't matter.
Oh, and to stay slightly on-topic: If longswords and katanas in Skyrim were made of the same material and used the same smithing techniques, then both blades would be roughly the same length and weight (with the longsword weighing more due to the massive sword guard). Both blades would be equally good against lightly armored enemies (slight edge to katana) and both would svck against plate-&chainmail when slashing (advantage to longsword when stabbing).
Tactically the longsword would be superior since the double edge and the swordguard allows for more maneuvers.
Also: http://www.youtube.com/watch?v=pXWxFaGSghc