The Yamaha P125 is a stage piano designed for high-quality sound production and a realistic playing feel. It features 88 hammer-action weighted keys, a variety of sounds and rhythms, and a variety of ports and controls.
The Yamaha P45 is also a stage piano, but it is a little more simply equipped than the P125. It has 88 weighted hammer-action keys, but fewer sounds and rhythms than the P125. It's also slightly cheaper than the P125.
Compared to the P125, the P45 offers fewer features and sounds, but is still a high-quality stage piano with a realistic feel and good sound production. If you're looking for a high-performance stage piano but aren't willing to pay for the full feature set of the P125, the P45 could be a good choice. It is important to note that both instruments are of high quality and may suit different needs and budgets.