By comparing the weight of the swords to each other, we can determine their speed, or vice versa. Differences in length can also effect the speed of the sword.
No, you cannot. Grab a pen (do it!) and swing it as fast as you can through the air. Now, grab 5 pens (same make/model) and swing them through the air. Did you swing 5 times slower? Our arms have a maximum speed at which they can swing. At low weights your arm will swing objects at roughly the same speed. Even if your muscles were able to contract at an infinite speed (again, they cannot), you'd need to take the weight of your arm(s) into account (including armor).
These sources indicate that the average weight of a human arm is 5% of the person's body weight. The average male weighs around 190 lbs (let's keep it in the ridiculous Imperial system because I believe that's the units Mount and Blade uses for weight). That means the average arm weighs 9.5 lbs. That means two human arms weigh 19 lbs. So, the ratio of the moving weight difference between the katana and the bastard sword is ACTUALLY 19 + 1.8 vs 19 + 1.25. That gives a ratio of 1.0272, which means the speed of the katana (given the bastard sword has a speed of 99)
should be approximately 101.7 (102 rounded up). Obviously this speed difference would reduce further as more weight is added to the arm due to armor.
This is completely ignoring that your concept of physics is "it is heavier, therefore slower". Grab a hammer by the head and flick it with your wrist. How fast does it swing? Now, grab the hammer by the bottom of the handle and flick it with your wrist. Notice that it swings considerably slower? Weight distribution greatly affects the speed of an object being swung.
As for the thrust; have you ever tried stabbing a tree with an axe (as in, grab it by the head and push)? Try the same thing with a knife (real knife, not a kitchen one, lest you break it). You'll notice the knife penetrates much further. The katana was designed for cutting, while hand and a half swords were designed for cutting AND stabbing. They have a very pointed tip, while the katana essentially has a a cutting edge for a tip. Because the bastard sword's tip has a much smaller surface area, much more pressure is applied to the area it contacts than would occur if the katana was used.
Please, come back when you've learnt some basic physics.