I'd suggest considering a LoG (Loop on Ground) antenna for a KiwiSDR. I usually have mine connected, except when there's substantial pirate activity, then I connect the 43m dipole as I figure most listeners to the radio are interested in pirates.
I've found my 350 ft LoG produces a very good signal, especially on MW, but does not overload the KiwiSDR (it does not have an attenuator). Previously I used the sky loop, but that often overloaded the KiwiSDR. I do have plans to build a splitter that only passes a portion of the signal to one port, and connected that to the KiwiSDR, the other port going to the netSDR, which does not suffer from overloading.
MDK2: I do not have a high noise environment here, but from reports of others that do and have tried a LoG, they said it worked remarkably well.
Update: I just built the splitter, seems to be working. I'll write up a short post in the Equipment board.