it all depends. formats may change for 2006, but aside from that... you need to decide which. in the paper based, your score is based upon comparisons to the pool of grades and where you fall. test questions may seem a little more difficult because 96% are probably new or just reworded. so, even if it is more difficult, that may be better since a lower grade may grant you a higher score when placed for raw scores. the more horrible people do, the better your score reflects, vice versa. in the CBT, the test is based on scores from a practice group of first-time takers (or some other form?). there may be a couple of repeat questions since they come from a pool, close to 10%. this can be an advantage if you study well your old tests, or disadvantage if you are not familiar with the repeat questions. this may leave you either up to par with other students or up to 10% behind. paper based gives advantage to no one while the CBT may give disadvantage if you dont know the easy questions everyone else is getting for free 😉 . either way, studying the right material will get you ahead.
there are a supposed 15% of trial questions that dont count in paper based, not sure if it applies to CBT also. and the paper based test you have december/july, and the results 30-40 days later. do you need results now or can you wait? thats up to you.