They will light in the cold, just slow.

The Fluorecsents may not below 40.

The MH will last a long time and throw more lumens (light output) per watt. They are more expensive to replace per bulb but you should get by w/ 4 or 6 w/ that size barns,

I have a 65 x 120 indoor arena with 10 400 watt MH fixtures. Have replaced 2 bulbs in 6 years.