The delay was very much inevitable regardless, owing to unexpectedly heavy spring flooding of major waterways, and incomplete deployments. Of the forces diverted for Marita (etc), about two-thirds were able to be instantly replaced with German reserves, and the others were en-route to rejoin the invasion by May.

But, on the other hand, the toll extracted on some important divisions shouldn't be underestimated, despite relatively modest losses - several important panzer and motorized divisions saw heavy losses in equipment and had to be placed into the reserve while they refitted, and didn't see combat until well into the later stages of the campaign in Russia. Given the very tight margins of the campaign, and the importance of mobile divisions, this may or may not have been very important in the larger scheme of things (hard to say). 12th Army was also diverted to occupation duty, instead of joining AGS, complicating the southern wing's job, which was the least successful aspect of the invasion, and eventually required the diversion of some AGC forces to Kiev, instead of pushing onto Moscow. Whether the early attack on Moscow was even possible at that point is highly debatable; I think not, myself - AGC was pinned-down by extremely heavy attacks, and Kiev was a colossal German success, without which the Moscow offensive was dubious. Finally, the invasion of Crete was a close-run thing, and took an enormous toll on the Luftwaffe's transport fleet (which would be very important later in '42) and paratroopers, and effectively ended the airborne menace for the rest of war (which had been very effective thus far).

The problem with either side of the argument is that they rely on a version of history that never happened, thus we can never really know for sure. Some assume that an earlier start to the invasion would have allowed the Wehrmacht to drive on Moscow before winter, but one can't be sure that the early stages of the invasion would have been as successful in Spring thaw conditions, or that the Wehrmacht even had the strength to take Moscow even under the best circumstances (IMO they did not). On the other hand, we can't know if the invasion wouldn't have been more successful had the handful of panzer divisions that took part in Marita been available from the beginning, or the elite German paratroops been used to break Soviet lines where they resisted most stubbornly. Either way, Greeks deserve to be proud of their record in resisting the Nazis when others stood-by or meekly capitulated without a fight. My Grandfather and his brothers fought in Crete, and had nothing but admiration for the Greek people as a whole - greetings from New Zealand!