The design of the Colt cylinder release had a specific purpose.
When Colt designed the basic release in 1889, most shooting was done in the classic "duelist" style with one hand, which became the classic target shooters high thumb hold.
The cylinder release allowed resting the thumb on the release. This not only gave a good high thumb rest position, it insured that the cylinder couldn't accidentally open under recoil.
Later Colt's made before WWII actually had checkered cylinder releases to give an even better thumb rest.
S&W operates by pushing the release. For that reason you can't use a S&W cylinder release as a thumb rest or the cylinder will open under recoil.
Early Pythons had lighter barrels then later guns.
The early models had hollow under lugs and the vent ribs. The vents not only lightened the barrel, it also looked like the very popular King's Target ribs that a lot of target shooters had installed on their Officer's Model Target revolvers.
As time passed, shooters ideas of what was too heavy changed, and Colt stopped doing the hollow lower lug barrel and went to a sold lug, making the barrel even heavier.
Reportedly, some target shooters had been putting lead bullets in the hollow lug to add weight to the barrel.
This was in the days when revolver and auto barrels started getting extremely heavy, leading to the massive bull barrels you see today.
Back in those days, most shooters would have thought the super heavy bull barrels just too much. Now you seldom see an actual target pistol without a heavy bull barrel and even extra accessory barrel weights.