I read so much bullshit in the threat about horses, stabs and stuff. As 1h on horseback for over 3 years, let me get you clear a pair of things:
1st: Stab doesnt outreach a slash attack. That is just simple bullshit. What you can do is tricking the enemy so you get closer than his slash in the last moment and stab. Sure thing its not something "easy to do". Its not that his "swing is shorter" its just htat the stabber will try to hit the slasher before his sword makes the full movement. If he fails he will get hit for tons of damage. Indeed, a 2h always have the edge in a combat vs a horse with 1h, even a 1h on ground. Just a bit of footwork and you kill 99% of riders (included me). Speed works both ways, sometimes it allows you to kill some guy, other times just dont allow you to avoid an attack.
2nd: 1h cavalry actually KILLS lancer cavalry. At least if you got the skills, if you dont kill him.. well you gonna make his life miserable coz you gonna be in his back for the rest of the round. (the spinning nerf on horseback is the lamest nerf ever made in this game i would say). In the past, lancing on horseback required skill. Nowadays is lame and just require some planning and picking unaware targets. The fact you cant trick the enemy with your "attack angle" means there is only on way of killing someone. So predictable. So, its this or taking an arab gay horse. This horse kinda counters the effect of the nerf, since it allows you to circle in a split second.
Just that. Btw, what kafein says is true. Going on horseback is mostly a handicap than an advantage in nowaday's crpg. Any player who is decent will perform much better on ground. Still, even being 1h forever, i admit 2h is best class still (i play all classes btw, even selfnerfed alts).