You cannot transpose from a major key to a minor key. You can change the key of a piece, but transposition must be either major or minor. Actually you can transpose from major to minor but it won't...
If you think about it, the answer seems fairly obvious - major. Samba tunes seem very joyful and uplifting, and major keys help create this effect. Minor keys normally give sad sombre sounds.
Major keys tend to sound happier and minor keys tend to sound dark or sad. Major keys have different patterns than minor keys if you start on the first note of the scale and play up the scale. I like...