Either is 'normal'. Personally I would not do either.
Your third option is this.
License the piece to the client. You create a piece and copyright it. You then write up a
legal agreement stating that for a fixed fee of £x client X is entitled to use the piece
for podcasts of X magazine. You take agreement to an entertainment Lawyer and make sure
that it is watertight.
As for how much? Pricing your work is the hardest part about being self employed! Factor
in the time taken to compose the piece, any other performers necessitated, studio time
(and lawyers fee)etc.. and what you think your piece is worth!
The beauty of
this proactive approach is that you are paid for your work but you retain all rights. If
you wish to use the theme or hook of the piece at a later date you may do so and unless
you state that the client has exclusive use, you can use the piece elsewhere. You can also
Put a limit on the time or state for the license must be renewed annually.
Royalties were devised so that when music or film was distributed by a number of outlets
(differing radio stations, TV, etc..) the artist would be paid. You are looking at a sole
distribution point for a singular piece. Don't overcomplicate things!