When I was building competition guns based on the 1911, I had some high-speed photography done to gauge various compensator designs I was doing. An unintended side benefit of this was quantifying slide cycle times.
On my Steel Challenge pistols, I lightened the slides so that the reduced power loads could function the pistol correctly/reliably. The stock 1911 slide simply had too much mass for reliable cycling, but the counter to that was by reducing too much mass you jeopardize the reliability of the cartridge strip/chamber loading of the next round. Always trade offs.
Lightening the slide on a 1911 design shooting .45 cal will increase the rearward velocity of the slide to some degree, but there have been many arguments about if it is even perceivable to the shooter on just in their head. The downside to this is that the increased rearward velocity can accelerate the wear of your frame unless appropriate steps are taken like shock buffs, stiffer recoil springs, etc.. I have found that one of the best ways to improve cycle times in a 1911 design is simply to reduce or eliminate movement in undesired vectors, or in simpler terms, get rid of the slop in the major moving pieces. I'm talking about fitting the slide to frame, barrel to slide, and barrel to frame to get the smoothest action possible. But at this point you could be way north of $2000 if you are having this done by someone else.
Now I'm talking about competition guns here with all this. This is not something I would do for carry or duty guns (I still have 45s being carried as duty weapons over 20 years after I built them). Reliability is first and foremost for a duty or carry weapon. IMO anyway...
But at the end of the day those slots do look cool, so if you like them go for it and don't worry about the cycle times.
My only caution at this point would be to be careful of violating the integrity of the slide. You don't want a piece of that thing coming back at your face in the event of catastrophic failure.
