It's not a matter of opinion. It's a matter of mechanics. A double action revolver will fire as fast as you pull the trigger, no matter how fast you pull the trigger.
An auto-loader, on the other hand, is out of battery and (I should hope) has the disconnector engaged between the time it takes to fire one round and chamber the next. If you pull the trigger during this time, nothing happens.
This is why all competition speed shooters (that I'm aware of at least) shoot revolvers.
Having said that, I also prefer a single action trigger.
That's a whole lot of energy being dumped into the mellon for it just to poke a hole through it. How far away were you?
At any rate, try the same experiment with your Enfield again, but this time use surplus military ball .303. That particular round, along with 5.56Nato, is the exception to the "Hollow point/soft point does more damage than jacketed" rule. It was intentionally designed to be back-heavy so that it more easily yaws when it hits a medium. I suspect the result of it hitting a watermelon would be pretty spectacular.