Mega Ray internal balast Vs external

[Mr Critter]

Building 6x4x3 enclosure,want to make sure i get right lights ,read all the info on rep. uv web site but would like input from those who use it.want to keep bulbs as far from tegu as possible ,durability,longevity,etc etc ,read that external balast mega ray eb60 is the best.any input would help