Elite cav is good, but knightly heater is better for horsemen IMO. I'd rather have the knightly heater on foot or horse, but elite cav is good on foot too. But I play in first person on horse, so the round shields cover up too much of my screen. Besides that, the knightly heater has better resistance, which is what you want (HP isn't that important compared to resistance).
For coverage, the regular heater shield (at level 3 difficulty) is also good bang for your buck. Not nearly as good as the 4 difficulty Elite Cav Shield, or Knightly Heater shield.