The best replacement for dual sim is single sim.

The best alternatives to dual sim are rated as following:
★★★★★  single sim
★  dual standby
★  samsung dual sim
  double sim

Your alternative for dual sim is not listed? Suggest!
Speaking about dual sim, one probably shouldn't forget about lte.

Other search terms related to dual sim and their ratings are:

★★★★★ lte
★★★★★ 4g
★★★★ camera mobile phone
★★★ camera nokia mobiles
★★★ camera mobiles
★★★ wifi phones
★★★ 3g mobile in india
★★ 3g mobiles
★★ android mobiles
★★ flash camera
wifi tv phone
wifi mobiles
qwerty keypad
camera phones
You have in mind a companion for dual sim and it is not yet here? Propose!

Google Trends

Scale is based on the average worldwide traffic of dual sim in all years. Click on graph for more.
dual sim
single sim
dual standby