I'd opt for the new setup.
I've had mine for several years now, and the solar panel is checked and oxidized. And in Ohio's humid conditions, no matter how well I try to seal around that bundle of wires, I still get mildew and tiny critters inside. That can't be good for the electronics. My transmitter is near the ground, though.
I'd found aftermarket sensors several years ago that we much cheaper than from Davis. I just looked, and I can't find where I got them, though. Sorry...