In general, there is no 'better' choice between one-piece and two-piece, and it comes down to personal preference. Obviously, if you're stringing a hybrid, you have to use two-piece!
For one-piece, roughly speaking the short side is used for half of the mains, whilst the long side does the other half plus the crosses. There are a number of variations, but that's the general rule. A good place to get an idea of length for each side is here:
Most manufacturers also have patterns on their websites.
Personally, I think two-piece is easier to follow when you're doing your first few string jobs.
If you haven't already, check out YULitle's YouTube channel:
He has some great videos that cover the majority of situations.
Enjoy your stringing!