I love fielding Hetzers -- for their cost, they bring a surprising amount of usefulness to the field.
That said, you have to remember that there are reasons these vehicles are so inexpensive. You do get what you pay for --- although in Battletech, that isn't always true --- you can pay huge BV points for a Hellstar and watch an opponent's Pack Hunter take it's head off on turn 2 of a game, prior to you hitting anything, as of yet.
However, with the Hetzer, the points are far more in line with what you get, and what is costs to lose the unit. And you will lose some, as they tend to get more attention than they may warrant, due to the AC/20. And they also tend to get pillboxed frequently enough, that the limited arc of fire can be hurtful.
On the other hand, they do bring an AC/20 to the field, and they do it at a cost that begs for it to be spammed.
As to the other variants, the LRM is the only other one I use -- and it is surprisingly useful..... being far more useful in most games, that would be apparent at first glance. For one thing, as has been pointed out, you get the LRM throw weight of a Catapult or Crusader, at the same general ground speed, but at a good chunk less than half the BV2 cost, and it has better ammo endurance. Now, you do have some terrain restrictions, but you also have the option of indirect fire, and a long enough range, you can fire from those areas you can get to. Lastly, this design is great for helping to offset the cost of TAG units on the field, or for carrying out specialty ammo, and acting as a support unit, to provide smoke, or minefields, as needed.
And while the Hunter is better in some areas, it is also more expensive, and sometimes, those extra points can make a big difference elsewhere, when building a unit. They both have their place... and neither is superior to the other.
Nahuris