If you plan on inletting the barrel yourself and it's your first build I would go with a straight barrel.
I started that way myself and now 4 rifles later (3 straight and 1 tapered barrel) I have mustered the "courage" to try inletting a swamp myself
Your first rifle will no doubt contain numerous mistakes - that is how you learn and improve. And if you are like me (don't really fully understand something until you have done it yourself at least once, no matter how much you read or watch), a straight barrel is a good way to learn.
You can move it back/forth a little to get the lock geometry correct once the barrel is inlet - you can't do that with a taper or swamp without leaving very visible gaps which would have to be hidden - again, once you have done it once you will know what to watch for/be careful around the next time.
Plus, you still can make some pretty nice rifles with a straight barrel - just pick something that would have had a straight barrel on the original so that it doesn't look like a "wannabe" rifle.
If you only plan on one rifle and the style you want really "needs" a swamped barrel, you could have the inlet done for you and take it from there.