RE: glow to electric conversion
About AXI at a glance:
4120/14 - bigger props (14"), more amperage (40-50A), 8000 - 9000 RPM, less cells count (voltage) - 16 cells;
4120/18 - smaller props (12"), more RPM (11000) less amperage (30-40A), more cells (voltage) - 20 cells.
4120/18 has more power then 4120/14 at high cells count (20-22 cells). But it is only 4120/14 you can use with 14 -16 cells (4120/14 has more power on 14-16 cells).