Answer: Euonymus alatus 'Compactus', the dwarf burning bush, would be a good choice for the site you describe. The mature height is 6'-8' with equal width. While it will grow taller than 4', you can keep the plants lower with annual pruning. It's adaptable to most soils and will tolerate drought once established. As an added bonus, the foliage turns an intense scarlet red in the autumn.
Berberis thunbergii 'Rose Glow' is a Japanese Barberry, with attractive red and white mottled foliage. Mature height is 5', which you can control with annual pruning.
'Angel Ring' Barberry produces bright purple leaves which turn red in the autumn. This shrub grows only 3'-4' tall and about 4' wide. It's the smallest of the plants you've mentioned and will fit the site without the requirement of annual pruning.
Hope the above provides you with enough information to make just the right decision for your new hedge!
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