The short version
Plunge is the premium category leader; Edge is the price-disciplined challenger with comparable hardware. The decision rests on whether the brand premium is worth $3,500 to you.
When The Plunge is the right pick
If you want the category-defining build with longest multi-year reliability data, marginal chiller-power edge, 3-year warranty and the founder content ecosystem — The Plunge is the right shape.
When Edge Tub is the right pick
If you want chiller-built cold-plunge capability at the most accessible price in the tier — Edge is the right shape. For typical home daily-use practice the hardware delivers what most users actually need.