Hi!
There's actually quite a lot - or maybe just a few but important - differences between the Bugaboo Cameleon 3 and the Bugaboo Fox2. The Fox is a higher-positioned, "taller" model, but it's also a newer model with more detailed construction and upgrades, even in the design. The seat and the carrycot part being higher are better for your back as well as for the view of the baby. The larger wheels - mainly the front ones that will make the biggest difference for your pushing - are so much closer to the original Bugaboo Buffalo, that is actually a predecessor of the Fox - and the Fox is closer to that all-terrain model than top the Cam... And there's the reversible handlebar on the Cameleon, which is, in my opinion, not a good thing - it's an obsolete function making the sturdiness of the joint worse, and not really helping that much because the driving with the reversed handle is not comfortable at all.
For me, the Fox is, by all means, a better choice and an overall better-functioning model, so I would certainly recommend getting a Fox over a Cam. It's just better in all aspects - it even folds with the chassis (and the Cameleon does not) 😉