We applied for a visitor extension for 100$ before one month of the visa expired (it is our 2nd visitor extension) we got it approved within a month and we got a year. We mentioned that we are planning to apply for sponsorship so in your case since you are already applied you will get it too.For a visitor extension, the current processing time is 85 days vs a Open work permit is like 135 days. So a much longer time that you have implied status when applying for OWP. Also OWP, I have never heard of a rejection for SOWP with AORs. And of course the biggest advantage is that your partner can work once approved and help with finances. The cost is more for a OWP but has more benefits if you ask me