Advantage of low voltage
The low voltage LED are always going to be more advantaged. The energy efficiency of the low voltage LED was high(Low voltage driver and low current consumption.), and along with the voltages increased the energy efficiency was dropping.
For example: the lumens of 1W white led is 100 lm

When VF is 3.0 : 3.0V X 350ma = 1.05W，light effect 100/1.05W = 95.23 lm
When VF is 3.4 : 3.4V X 350ma = 1.19W，light effect 100/1. 19W = 84.03 lm
The upper data structure table is only for your reference, we know that Exercise consumption of energy resources when vf rising.