Which sounds more positive

While both words mean "spending carefully", a "thrifty" woman spends money wisely while a "frugal" woman spends money only when absolutely necessary.

Thrift: This is considered a virtue, though many consider it an old-fashioned virtue. Definitely positive.

We live in a "consumer society", and thriftiness is not encouraged by commercial enterprises which pursue consumption and profit as their goals.

Frugality: This is thrift taken to an extreme, verging on miserliness. At an extreme, this could be a polite way of referring to somebody with "cheapskate" (very negative) tendencies. Neutral, but going in the direction of negative.

Thift is a chosen virtue. Frugality may be a bitter necessity.