They're comparable from the power standpoint, but the deciding factors, as almost always, are the features which you prefer. The 43TX has already dropped into the $500 area since it's being replaced by the 53TX. Whenever the 3804 is officially announced the same will happen wih the 3803.

In that price range I'd suggest the 53TX instead of either, since it's been upgraded with automatic MCACC. Another possibility is the new Yamaha 1400.

-----------------------------------

Enjoy the music, not the equipment.