Generally, new motors are in fact more efficient than old motors. There have been Government subsidized programs in effect to increase motor efficiency throughout industry for the last 10 years. Manufacturers who didn't take advantage of the help found themselves behind the eight ball a long time ago.
That said, HP ratings on consumer products have been a big "spin" game for a long time and there are ongoing lawsuits over this issue. I wouldn't trust them as far as I could spit. If you are not referring to a residential consumer product, you are probably OK. If you are, the better way is to look at speed and torque since that is what really matters. If the motor does not provide that information, be suspicious.
I don't know if they are NEMA rated. They're Emerson and GE brand names if that helps. The hp rating is from the manufacturer, not some homeowner promotional literature. Should I not trust motor data plate information on fractional hp motors?