Here is a good summary, said better than I could concisely articulate......
"A/B ratios are controversial. Some naval architects take issue with the entire concept. Critics correctly observe that the factors considered in stability studies don’t include an A/B ratio. The factors do, however, consider a vessel’s center of gravity. The lower the center of gravity in the hull, the less likely a boat will rock excessively in a beam sea or capsize. Voluminous superstructures perched on a shoal draft hull are more likely to have a higher center of gravity.
A high A/B ratio will have some ramifications that are completely separate from stability. The greater the amount of surface above the waterline, the more “sail area” is subjected to wind to confound close quarter maneuvering. On the positive side, more mass above the waterline permits cabins with more headroom and larger windows, and may even raise the main deck enough to increase the vertical clearance in the engine room.
The sea is no respecter of brand names. Storms do not defer to ad campaigns or marketing hype. Informed and intelligent selection of an ocean going trawler intended for long range cruising can be somewhat simplified by comparing and contrasting the afore-mentioned ratios and understanding their effects on predictive performance of a hull."