"Very" heavy? Maybe once you get into the all-metal frames, but for the polymer guns I can't say that I remember any significant difference that affected my shooting (though since I'm still a beginner, it's not like I have great precision in the first place).

I shot a S&W M&P M2.0 full size (4.5"? 5"?), CZ P-10 C, and Walther PDP Compact 4" during my first day of testing.

I had the best accuracy with the full size M&P, but I assumed that had more to do with the barrel length (all three were iron sights, no red dots).