In the early 1980s, I instructed on PA-44 Seminoles. We had two blades per engine on the first two aircraft and then took delivery of a new aircraft with three blades on the props. This was a new option introduced by Piper for that year's model.
The AFM had data for both two-blade and three-blade props. I remember being surprised that the three-blade data showed, in comparison with two blades:
1. Noisier;
2. Slower; and
3. Heavier.
Having spoken with the Piper dealers, the only reason we could come up with for the three-blade option was that it looked better on the ramp! I suppose there was a small benefit from the smaller diameter prop as well, being less prone to ground strikes and stone damage when taxying between grass/tarmac.