Though of course if you make them Terminators, they not only become more expensive individually, they also take up more space in the drop pod. Whether this would be offset by the better durability or not depends on the enemy you'd be facing.
And them being Troops requires one particular, fairly expensive Special Character. Though I guess except for the "expensive"-part, this is true for Sternguard as well (apart from the difference between 'Troops' and 'scoring').