Ok so let's update.
Marshall out of the equation.
Clarke > Strauss in limited overs, no point even looking at that.
For the last 2 years they have both had great records when you take in to account the positions they bat.
Strauss - 25 matches, 1939 runs @ 48.47, 7 centuries
Clarke - 27 matches, 2268 @ 56.70, 8 centuries
Over their careers, Clarke averages 51 to Strauss' 43 but Clarke is more likely to get not outs. Strauss has 18 centuries to Clarke's 14, but as an opener he has more opportunities, in fact he has 34 more innings to his name than Clarke.
They both had strong Ashes series last time they met. Clarke averaging 64 with 2 centuries, Strauss 52 with 1 century.
Before the Ashes Strauss came up against WI in two matches and averaged 24 with a top score of 26. Clarke played WI after the Ashes and averaged 52, collecting 2 half centuries with a top score of 71.
Strauss then came up against SA and averaged 24 again, crossing 50 once for his top score at 54. Clarke collected similar stats when he toured SA last.
Recently Clarke has hit back to back centuries against Pakistan and NZ, Strauss hasn't made a century since the last Ashes, I betting he will get a few this English summer though with Test matches against Bangladesh and Pakistan coming up.
Clarke > Strauss.