"prone to" carries a negative connotation, while "tends to" is more neutral

There is more than one meaning for "tend " and "prone to" Meanings of "tend" aid, attendance, attention, care, remedy, tending, therapy, treatment, attend, be inclined to, be inclined towards, have a tendency to, incline to, incline towards, lean to, lean towards, look after, medicate, nurse, treat. Meanings of "prone to" = likely to do something OR be affected by something, vulnerable. Examples: 1.The coastal region is prone to earthquakes. 2.prone to do something: He’s prone to gain weight. 3.error-/injury-prone: He's an injury-prone football player

prone = vulnerable to tend = lean towards