The bass guitar is founded on electric guitar technology, so it’s not surprising that its strings share the same basic materials - nickel-alloy, nickel-steel and stainless steel. As with the guitar, roundwound strings are generally favoured by rock players, while jazz players often use flatwound strings, particularly on fretless basses. |
Again, sets vary a little between manufacturers, but the chart below gives a general picture:
As with all strings, there’s a trade-off between tone/volume and playability - heavier strings sound better but can be harder to play, especially for beginners.