Whether Germany gets involved militarily or not in the Balkans is debatable, the need was to protect their southern flank and especially the Ploesti oilfields. But with no British involvement with Greece - no problem.
For the Germans it means:
- no diversion of resources to aid the Italians,
- no diversion of the Afrika Korp (and Rommel) to Libya,
- no squandering of the airborne troops at Crete - now available for prime targets in Russia,
- no diversions for the Luftwaffe, which can concentrate on the Russian Front, and keeping the British busy,
- when they do meet British forces again it is without the live-training camp that was North Africa!
For the British it means:
- access to Italian equipment - engines for RN MTBs, Caproni CA 311 & 313 aircraft as trainers, and possibly the Re. 2000,
- access made easier to India through the Med.,
- the British Army doesn't get the tutorial it needs in modern war in the desert of North Africa,
- with out the distraction of the Italians the British will still do what they can to stir up problems for the Germans in the Balkans.
- likewise, without the distraction of the Italians the RN can concentrate its efforts against the U-boats, German surface ships, and Japan.
- but where are the British going to be able to bring the Germans to battle?