The ps4 hard disk from factory has a speed of 5400rpm vs a SSD w is about 57000rpm could be more or could be less depending on brand, I guess you wanna upgrade the hard disk because of the loading screen, so yes upgrading to an SSD will improve the load speed a bit,you need to know that a loading screen is more affected by RAM an CPU that an actual hard disk upgrade an the ps4 is limited on that so you will not see a big difference, my advice is to leave it as it is,the most you will get will be about 15-20% from an upgrade about the 150.00 or more but then again is your decision.