There is no good answer to this question. Since NCARB switched from Prometric to PSI we have heard mostly negative reviews. The testing centers seem to be sub-par, their equipment does not meet NCARBs stated requirements, and there are reports of many technical issues. There are fewer PSI locations and some candidates are having to travel far distances. Try to find out about your specific test center location from friends and colleagues, google, or visit if possible, it may help with your decision.
The Online testing seems to invoke fewer complaints. However, it requires some preparation on your part. You need to evaluate your internet connection, equipment, room set-up, and perhaps purchase an external camera. There are a lot of rules you need to review to test successfully. Lastly schedule practice runs to make sure everything is working well before you actually test. If all goes well the benefits are many. You can find more information on NCARB's website.