Quick take
Choose Hydro 4 SE when you want the lower entry price and corded full-pool cleaning. Choose Hydro 4 when the feature differences on the current model justify the price premium for your pool.
Corded architecture
Hydro 4 SE is a corded robot, not a cordless model. That gives it continuous power at the cost of cable management.
Cleaning coverage
Hydro 4 SE targets floor, wall and waterline cleaning with app control and dual-zone filtration.
Price gap
Hydro 4 SE has been positioned around the mid-$400 range, while Hydro 4 is typically higher. Current promotional pricing can narrow or widen the gap.
Who should buy the SE
Budget-sensitive buyers who still want wall/waterline cleaning may find the SE the better value.