Hi.
The string-through body design.
On "short" (from the anchor to the saddle) bridges the string through helps to prevent the unevenly wound portion of the string resting on the saddle.
Stringing through also usually increases the break angle over the saddles, and can prevent uneven saddle pressure between the strings.
Since the break angle increases, one has to be extra careful when using flatwound or half round strings, they may break on sharp saddles.
Since the strings ability to spin freely is severly restricted when using string through, one has to pay attention not to twist the string when restringing.
Some bridge designs and also some body wood choices can benefit from string through since the strings press the bridge tighter onto the body, instead of trying to pry the back of the bridge from the body.
String through usually requires a bit longer string than a top load, which may pose a problem. Or at least limit the available choices.
String through usually somewhat restricts the intonation adjustment, especially on mono-rail bridges, so going BEAD or F#BEA on a four banger may require a combination of string through and top load.
IMO, and IMO only, string through looks cleaner and somewhat better than top load.
Most of my basses and guitars are top load though.
The sonic differences between string through and top load I won't touch with a ten foot pole

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Regards
Sam