Below there are some comparisons.
Comparison n.1
Even though both networks position themselves similarly in the IoT market, they have significant technological and marketing differences.
While SigFox aims to become a global IoT operator, LoRa alliance wants to provide a technology that allows other companies to enable a global IoT.
Neither SigFox nor LoRa offer encrypted communications
(From: Raed’s Blog)
Comparison n.2
Coverage
LoRa: less than 14 Km
Sigfox: less than 17 Km
Signal Bandwidth
LoRa: on CSS (Chirp spread spectrum)
Sigfox: on UNB (Ultra narrowband) — higher spectral efficiency and can mitigate the noise better
Usage
LoRa: uses more bandwidth
Sigfox: is very practical for infrequent transmissions and offers longer battery life
Business Model
LoRa: can by deployed on your own to just cover your local area
Sigfox: is a network operator, so you wait for them to deploy, and you pay a subscription fee
Security
LoRa: weaker compared to Sigfox but I believe it will be improving
Sigfox: is better in preventing replay and man-in-the-middle attacks
(From: Annie’s Moment)
Comparison n.3
(From: Rakon)