Web-based practice tests versus soft-copy or printed tests

Getting a PMP certification requires a 200-question examination taken through a local controlled testing center. The test is automated, timed and you get your results immediately after the test.  By special request it can also be offered in a printed version. But what about taking practice tests?  Is it better to take them online or using a paper copy or soft-copy version of the test? The online version should provide immediate results. It may offer time limits and some tests offer breakout grading by process groups or selected knowledge areas.  There are some pay-testing sites that let you review your answers days or weeks after taking the test.  Most online mobile applications don’t offer this feature. A paper copy can be taken without any device.  A soft-copy test can be taken via a computer or tablet screen and gives you unlimited time, unless you time yourself. Any of these three allows you to stop and start anywhere during the test. Grading is probably manual and you probably won’t get any feedback on process groups or knowledge area question types. With a paper or electronic copy you can review questions at your leisure.  Each have their pros and cons.  Which do you think is better?