In terms of the big 4 from the 80s...it depends entirely on what criteria you use to rate them.
At their very best, I'd probably choose Botham....
However, if I was reflecting over their entire Test careers as all-rounders I'd rate them something like;
1) Imran
Batting - For periods at the back end of his career was good enough to be selected for his batting alone, scored 6 hundreds & averaged late-30s - As a test batman 7.5
Bowling - A magnificent bowler who had it all; pace, swing, seam, control along with an intelligent mind. As a test bowler 9
Imran Total 16.5
2) Botham
Batting - Despite averaging 3-4 runs less than Imran with the bat, lets not forget he scored 14 test hundreds & at his best played some of the most memorable game-changing innings in Test history. Like Imran, for periods could have made it purely for his batting. 7.5
Bowling - His bowling career was one of two-halves. It's easy to forget what a great swing bowler Botham was in his early days, used to get it going really late, even before reverse swing was known as it is today. However in judging their whole careers, I need to consider his decline as a bowler. Overall bowling 8
Botham Total 15.5
3) Hadlee
Batting - Definitely the weakest batsman of the 4 & unlike Botham & Imran he wasn't good enough to make it purely as a batsman for much of his career. Whilst he did improve to average over 30 throughout the 2nd half of his career, in the final wash scored just 2 hundreds (& a 99). Overall batting 5.5
Bowling - An absolute Rolls Royce of fast bowlers (only 2nd to the great Marshall in my humble one-eyed NZ opinion ) who cut down his action and mastered the art of swing & seam bowling 9.5
Hadlee total 15
4) Kapil
Batting - Overall, I have him slightly behind Botham & Imran with the bat. For those that didn't see much of him, was a magnificent striker of the ball who did score 6 hundreds & averaged around 30 in the final wash 6.5
Bowling - It must be noted that he played much of his career on dry dung-heaps, although would still rate him as the weakest of the 4 when it comes to bowling. Had a magnificent action & could be a devastating swing bowler in the right conditions 7.5
Kapil total 14