Gregable
Consider having the sliders even in the not-married case
If the user selects not married, there are no sliders. However as simple as the output/graphic might be, the slider is an interactive element that illustrates the early and delayed benefits nicely, even if a chart/table is sufficient. Especially now that you've illustrated the effect of delayed credits which are not fully applied at first.
Do you feel like it adds much value beyond the line chart in the "Early and Delayed Retirement" section?
I suppose that chart doesn't marry years and ages as nicely, however, you can see the entire glide slope on a single chart there rather than needing to move the sliders around to understand the impact.
Do you feel like it adds much value beyond the line chart in the "Early and Delayed Retirement" section?
No. I don't feel strongly about it. But I don't think it detracts at all and allows for visualizing the delay in the delayed credit payments. Minor thing either way.