Some Ultrabooks are shipping with the slower 10 W GeForce MX250 instead of the "regular" 25 W GeForce MX250. Worst yet, it's almost impossible to find out which before purchasing. The 10 W version is expected to perform about 30 percent slower than the 25 W version based on what we've seen from the MX150 series.
https://www.notebookcheck.net/Sneaky-Nvidia-the-slower-GeForce-MX250-Max-Q-1D52-exists-and-they-aren-t-telling-you.415769.0.html