Limelight produces blooms that are more white than Little Lime. But a bigger, better root system easily produces a much larger plant. After a few years of getting established, I would see how the plants have grown and prune them to get the more in sync. The are other reasons that could also account for the size difference.

I have 2 little limes that are growing at different rates. They are young.

I also have 1 limelight that is substantially bigger than either of the little limes, and it was planted at the same time.