If you are a new shooter and this gun is new to you, I'd recommend that you shoot it (a lot) before modifying anything. Everyone's preferences are different, and you may find that you like a heavier gun. They tend to shoot flatter and make it easier to follow the sights, or in your case dot.
The big advantages of a lightened slide are that the gun cycles faster and transitions from one target to the next are faster. These are 2 things that shave off a few hundredths of a second and really only make a big difference for shooters that are very experienced and have all of the fundamentals absolutely down.
Before I make any modification to my competition guns, I ask myself two questions: Will this give me a significant advantage? Will this make shooting or practicing easier?