Wireless electronic dog fences fall into the category of aversive dog training, and as such discussion of them is not permitted on this forum. There are many reasons why they are not a good idea as a means of containing your dog.

Please read the following to inform yourself of the dangers of electronic fencing.
Invisible Fence, electric fences | Dog Forum
Electric Fences | Positively.com

 

Madra Anamchara beat me to it. The answer is none of them. Here is a thread discussing why: https://www.dogforum.com/threads/invisible-fence-electric-fences.369987/

You might also want to review the forum rules:
Respect the forum's posting guidelines regarding training methods. DogForum.com promotes a force free training philosophy based on learning theory and scientific research. We also promote educated debate on training methods. It is ok to discuss the merits of different training equipment as well as techniques, but it is NOT ok to promote or suggest any training equipment or technique that uses fear, pain, intimidation or is based in positive punishment ("P+"of the 4 quadrants).