Bond Street has an OSI to Oxford Circus. That route is going to be the fastest, provided that you know what you are doing when going between stations near Oxford Street.
Via Highbury & Islington is about 1km longer than the route via Oxford Circus and isn’t as fast on top of that*. It therefore takes a little longer via H&I. You have two 15 minute train journey going via Highbury & Islington. Via Oxford Street it’s 20 minutes on the Central line and 7 on the Victoria line. There’s obvious the times to get to/between/from trains that I’ve not included, plus wait times will be higher on the Overground vs the Central line.
*30 minutes to do 16.2km (ave speed 32.4km/h), vs 27 minutes to do 15.3km (ave speed 34km/h)
PS: via Tottenham Hale is 10 minutes + 24 minutes. 34 minutes to do 22.4km (ave speed 39.5km/h) – it’s the fastest average speed, but, by far, the longest route, and so it takes the most time. It also has the least frequent leg (4tph heading north out of Stratford). But it’s not a silly route – it avoids changing at the busy and cramped stations that are H&I / Oxford Circus and it doesn’t take that much more time.