Replying to Sony 18-200 VS Tamron 70-200

Whatsup Ns,

Through an amazing stroke of look I recently got an FS700 (with the sony 18-200 kit lens). I posted a thread asking about external recorders, but honestly I think I should invest in lenses.

I was thinking about the tamron 70-200 with a metabones speed booster. I was wondering if it would even be worth it to get the 70-200, because the sony 18-200 is already pretty good and has image stabilization. Obviously the 70-200 with the speed booster would be superior in low light situations (which I find myself in a lot)