I ride a 53t biopace with 17t, 18t and 19t cogs, which give me 82, 77 and 72 gear inches, respectively.

I have lots of chainrings and cogs, and I periodically put on a round ring and a cog that will give me gear inches comparable to my biopace combo, just to refresh my mind on the differences.

I prefer the biopace on subjective grounds.
It feels better to me.
My spin feels rounder and less up-and-down, and the overall effect seems like it buys me two free gear inches.

I tighten my chain so that I have just a tiny bit of play at the tightest point, which gives me about 5/8" play at the loosest point.
I really focus on my spin, and so I don't feel any slack anywhere.

For winter, I ride with the 19t cog at 72 gear inches, so I can stay off my front brake.
At 72 gear inches and a biopace ring (feels like 70 gear inches), I can easily brake with just my legs, without skidding.
I just slow down and stop.

So-called "scientific studies" indicate that the watts work out the same, whether biopace or round, but subjectively, to me, the biopace feels smoother, rounder, and easier.

If I wear out this biopace ring and can't replace it, I'll go back to round rings and enjoy riding my bike.