I have noticed this too. But dont have the luxury of two sims.My iPhone 12 Pro has 2 sims. Only 1 is 5G capable. I can switch data between the 2 sims. 5G is sometimes faster, and sometimes so jammed up, I switch to 4G Just to get functionality.
I have a standard iPhone 13, at times on the 5g network in crowded areas, webpages will "hang" with horrible service. Even though I could have two bars. It's not often but happens and annoying, 5g still has a way to go.
A good LTE on a cell phone is just as good to me. Sure it's fun to run a speed test on a strong 5G signal, sometimes freaking amazing highest I ever recorded was around 700 Mbps. But in actually use I have no clue as to speed on a cell phone, its always fast except as mentioned.