The PA 150 is a 12 volt DC, 1 amp power supply.

The Yamaha PA150 is 12 Volt, 1.5A (as the name implies)

A device will not draw more current than it needs. The 1.5A is deemed sufficient for the MODX.

You can look up photos of each on the net to verify.

Highly recommended!

The PA150B is a universal power supply (100-240V). This means it has a swap-able connector. In Japan, where they run on 100V, the PA150 comes with the appropriate connector to plug into the wall in Japan. In the USA, where the voltage is 110-120V, it comes with the appropriate connector to plug into the wall here. In Europe, where the voltage is 220-240, you can use the same PA150, just swap the plug connector.

The only difference between the Yamaha PA150 and PA150B is the swap-able wall connector. If you are in the USA, you can safely purchase a Yamaha PA150 as a backup to your (provided) universal PA150B.
The product shipped to your part of the world will, typically, come with the appropriate plug section already attached.

Disclaimer: this is based on what is provided here, your mileage may differ concerning which plug connector is included (check with your regional Yamaha distributor listed in the back of the Owner’s Manual)