Nothing wrong with the old standalone WDH and add-on sway control. I don't think I would upgrade just to upgrade. But if upgrading from a popup (for example) to something that needs WDH, getting integrated sway control is only a minor cost increase (Equa-l-izer or Dual-Cam), and worth it for simplicity.
thebrakeman ('70), DW ('71), DD ('99), DD ('01), DD ('05)
2004 Surveyor SV261T (UltraLite Bunkhouse Hybrid)
2006 Mercury Mountaineer V8 AWD Premier
Equal-i-zer WDH (10k), Prodigy Brake Controller