What are the strengths and weakness of each of the following Pistol Kits for a newbie.

Laymans Plains Pistol
1:30 twist. Anybody know the barrel length?

Traditions Kentucky Pistol
1:20 twist 10 inch barrel

Traditions Trapper Pistol
1:20 twist 9 3/4 icnh barel

Assume the user wants to shoot the pistol, and possible hunt with it. (not going to be awall hanger)

First off.. if I were going to hunt with any of them pistols you mentioned, I would sit down and seriously think about it. You are limited in distance you can shoot, power, and accuracy as you will find out. These are 25 yard and under pistols and that's with a good rest. Also check your state laws and make sure they are legal. Some states do not allow large game hunting with them.

If I wanted to hunt, I would get a Tradition's Buckhunter Pro which is nothing like these horse pistols. If you want to small game hunt, a .44 caliber black powder revolver works just fine. If you want to plink, then about anything will do.

lets taking hunting out of the equation then, what the pros and cons of the pistols listed for target shooting.

How does the twist rate affect accuracy?

In those shortbarrels the rate of twist will not be as critical because you will not be shooting long distances. Basically the 1-20 twist will produce a faster spin on the projectile in the short barrel then the 1-30 twist of the Lyman Great Plains Pistol. Both of them will shoot roundball well. I personally would take the Lyman Pistol. Also I would take it in .54 caliber. If I have to throw a ball at something, might as well make as big a hole as possible.

I have a friend that shoots a Lyman Great Plains Pistol. It is very well built, can take a pretty good load, and is accurate as pistols go.

The other thing to consider is parts and repair, in this case I think the Tradition's might have the advantage. I never owned a Tradition's pistol.

Years ago I had a Jukar .45 caliber horse pistol. With 20 grains of 3f powder and ball, it would hit a man size target at 15 yards every time. Was a lot of fun to shoot, but poorly made. I traded that off for something I thought I needed at the time.

I have a .50 Lyman Plains pistol and it shoots very well. It handles round balls well, plus I have shot Lee REALs & Lee modern minis through it and it handles them accurately.
I did change the sights to fiber optics (the kit for the rifle worked on the pistol) and it made it a lot easier to hit the target when I can see the sights.

Wabi, can you tell me how long the barrel is on your plains pistol?

Not 100% sure how to measure a muzzleloader barrel, but from the face of the breech plug to the muzzle is 8" (actual rifled portion of the barrel).
I might add that Lyman lists only a load for a .490 patched round ball - 40 grains fffg max. I've shot conicals, but wouldn't recommend others do it as it's not a listed safe load.
Now, with the disclaimer added I must admit a 320 grain Lee REAL ahead of 40 grains fffg is pretty accurate out of my pistol, and what I carry in it when I carry it on the trapline.