What's the difference in signal strength between bluetooth and wifi? I had assumed since they use the same frequency, and usually the same chip and antenna, they would be much the same (perhaps there are regulatory differences between them?) If anything, I'd guess that BLE would be more useful in this case as there is less handshaking, which means on a very poor connection you've got more of a chance of getting some…
On the other hand, i can walk an entire day through the forest (with some other people around every now and then) without a single position update from the tag.