I never really understand these. You aren't asking about mechanics. What is good or bad is very situational and subjective.
The best advice you will probably receive is to find a play style you enjoy, and MAKE it viable and fun.
I've always liked 1h cavalry, and always come back to it.
Personally, I prefer agility to strength and never go over 15 strength.
If you don't plan on having any athletics however, it would make sense for you to invest in just enough riding to get your horse and the rest into strength. A champion horse is more than enough to get around most enemy cavalry.
1h Cavalry is great to pick of unorganized, unaware, hardly armored/armed peasants and afks. Anyone aware of you that has any experience can easily out range, out maneuver, and deal more damage to you in each engagement. 1h cav is probably best played as infantry support. You are able to pick off those who retreat your infantry, and get behind those who remain to fight. The enemy archers will target you instead of your infantry, which is usually a good thing. Overall, 1h cav is a team class, not a solo k/d class. If you plan on working with your team, or if you have an organized clan, this class will always be viable.
As for choice of lance, it again depends on your role. Great Lances are very powerful, but very vulnerable. It is best to great lance in formation with other cavalry teamates.
Most of the highly skilled cavalry players default to using the Heavy Lance. The cavalry metagame is not about how much damage you can do, it is about how much damage you can do without taking any damage at all from anything (with the exception of range). Therefore, length is more important than raw damage. The Great Lance is the longest on paper, but swinging a lance adds length to it, making the Heavy Lance the highest length potential of all lances. IE: If a Great Lancer is jousting towards you and you have a Heavy Lance, if you time it correctly, you will always hit them first. Few players are familiar with the lengths and timing, and it takes getting used to.
With all cavalry builds, the metagame revolves around length knowledge and map awareness. Not just your weapons, but enemy weapons also.
Of course, some people can't be bothered to get good at cavalry and exclusively only charge people who are unaware. This won't help them against enemy cavalry though.
If you plan on only going for unaware targets, then it is probably best to get the high damage "Lance" or Great Lance. I'd recommend the "Lance" for novices. Couching has its own learning curve and being forced to dedicate to a forward charge to deal damage costs most novices their lives.
So:
1h cav if you wish to be a team player and not get too aggressive.
Heavy Lance if you wish to be a strong all-purpose cavalry player.
Lance if you wish to be ninja cav and only sneak up on people.
Great Lance if you want to familiarize yourself with the various weapon lengths and typical footwork of evading infantry.
Of course, you could always be 1h cav and carry any of those lances.
My preferred build is: 15/21
But you could go 18/21 if you didn't care about athletics.
Keep in mind, whatever you get good at, people will hate you for it.