I would do # 4 the extended version..because then u could go over ur answers...n ull be surprised as to how many similar questions u might see on the actual exam...people always say this one's harder n that one's easier....who knows what type of exam ur gonna get on the actual day....i think all of them give pretty good indicators of what u know @ the pt in time where u take them...my advise...take #4 1st.....the extended version...where u can go over the wrong answers....n then go over u weak areas for 2 weeks...n take another one....n then go over the weak areas again for 2 weeks....ull get around the same score as the last NBME...or do even better...if u drop...it will be like no more than 10pts...but with that u have to take into account the actual test is 9 hours...so that has to measure in somewhere...