Is the difference from PRO <-> Samsung 840 EVO 250GB worth it?
The PRO 256GB is 190$ and the EVO 250GB is 140$
Depends on what you're doing. For most consumers, no. It doubles the write speed from 250 MB/s to 500 MB/s. The read speed is 500 MB/s. Video games might install a few seconds faster after it downloads for several minutes to hours. The bottleneck isn't write speed usually.
But if you're doing stuff like video editing it might.
At work it makes a huge difference with software builds that output tens of thousands of files that net over 5 GiB.
It's frustrating too because sometimes the apps with the biggest potential benefit aren't optimized to use the SSD's write speed. Like disk cloning for example. Typically the imaging software, the network driver, or some other mundane thing is the bottleneck.