Sabre's in Korea had pretty much six .50 cal guns, the 20mm cannon don't show up until until late and then in limited numbers for test. Cannon armed Sabres , eight in number arrived in Korea in Jan 1953. They managed 282 combat sorties before the armistice in July 1953. No F-86Hs were issued to active squadrons, even in the US, until 1954.
However the six .50 cal guns in the Sabre's were not WW II guns. They were the M3 model that fired at around 1100-1200rpm or almost 50% faster than WW II guns. They also fired different ammo. The M23 incendiary round was a large part of the ammo load. I am not sure if it reached 100%. The M23 had about 500fpm more velocity but was essentially an incendiary round with NO armor piercing ability. It did carry 5.8 grams of incendiary material though.
The Meteor used MK V Hispanos which fired at about 720rpm which is better than most of the WW II Hispanos ( Tempests got the MK V) and at some point after WW II the British switched to aluminum fuses instead of brass for the 20mm HE rounds which made them lighter and improved velocity a bit.
Difference in climb was probably marginal. Yes the Meteor had better power to weight but climb is not
just power to weight. It is power to weight
AFTER you take out the power needed to maintain climb speed
AND the power needed to
overcome the extra drag of the aircraft flying at what ever incidence (angle of attack) was needed to get the climb rate desired.
The Meteor, being a much higher drag aircraft, was using a lot of it's extra power to fight the extra drag. Both planes, according to published specifications, had a very similar initial climb rate. I sure wouldn't bet much on a 3-5% difference in published figures as individual production planes could vary around 3% from each other when new.
However climb rate was very dependent on weight. 1954 Jane's gives the following figures for 3 different Meteors.
T. MK 7 at .......14,140lbs......8,000fpm at sea level
F. MK 8 at....... 15,675lbs......7,000fpm at sea level
PR, MK 10 at.. 17,345lbs......6,050fpm at sea level. This version reverted to the full span wings of the early MK III. which added 3-4,000ft to the ceiling.
Performance for F-86 versions can be found here:
Sabre vs MiG
I would take the service ceiling numbers with a grain of salt (or more) and would note that the higher powered -27 engine didn't make into service in Korea until June of 1952 and then in increasing numbers until the armistice the next summer.