[werk_ag]

If you remove the plastic on both of them, I'm almost sure you find the same thing inside, just a very small coil.
if you gonna change your antenna, and you are planning attaching it directly on the RX board, try a model with a right angle connector. For a unit placed on the roof, I always get better results with the antenna in horizontal than in vertical position, and don't forget that 433mhz is very directional, the better you position your antenna regarding the position of your RX unit, the better the results.