Golem has 2000 hp (stone), 45 armor, 10 range, 200 impact damage * 0.6 Hz, 3 hp/s regeneration
Behemoth has 5000 hp (organic), 50 armor, 1 range, 325 impact damage * 0.75 Hz, 5 hp/s regeneration
Against non-impact attacks, 2000 stone hp (0.5 multiplier) is equivalent to 4000 hp, and 5000 organic hp (1.25 multiplier) is equivalent to 4000 hp, so golem and behemoth have basically the same damage absorption ability.
Range isn't really useful for the golem; its attack strength is only approximately that of one battlemage, and its purpose is to absorb damage, not to deal damage. Behemoth is much more useful for absorbing damage since golem is too slow to even get into a battle, unless the battle comes to it.
And if it's a defensive situation, the summoner guild is the best unit for taking damage. 7000 stone hp, cheaper than golem, and gets built faster too. It doesn't attack, but that doesn't matter.
So in my opinion there is almost no reason to build golems.
Golem:
+ can be repaired (rate: 7 hp/s/initiate)
+ has large range
+ can hold position
+ regenerates faster than behemoth (golem: 3 hp/s (stone)=6 hp/s; behemoth: 5 hp/s (organic) = 4 hp/s)
- can't move well
- does not do much damage
Behemoth:
+ can move much faster than the golem can
+ levels up in 5 kills, vs 10 kills for golem
+ does twice as much damage as golem
+ tougher against impact attacks
- can't be repaired
- short range
- can't hold position (but this is not very useful for short-ranged units)
- needs Hell Gate to be built
Summoner Guild:
+ 7000 stone hp
+ can be repaired (rate: 35 hp/s/initiate)
+ built quickly (about 1 minute at 105 hp/s)
+ can be built from the beginning of the game
+ cheap
+ can store wood
+ can make summoners
- no armor
- does not regenerate
- does not attack
- does not move
