at the moment, i heard none.
in my own understanding, dual 3g/4g means, either sim 1 or sim 2 can use 3g or 4g at a time, not simultaneous.
other phone with no dual 3g/4g, means only sim 1 can use 3g/4g. and thats what my lenovo a536 is.
so dual 3g/4g doesnt mean you can use 3g/4g simultaneously in sim 1 and sim 2.
i am open for correction.