Herzlos

I've been looking at a new bike next year and have largely narrowed it down to a Giant Contend AR (for today, at least).
There are 2 models in particular, the AR4 (£899) and AR3 (£999), the only difference seems to be that the AR4 has Claris gears and the AR3 has Sora. I'd be using the cycle to work scheme so the difference is more like £75, however I already have 2 bikes with Claris components.

Would I realistically notice a difference between the drivetrains? Is it worth the price difference or am I best sticking with Claris and taking advantage of being able to share parts between bikes?

Thanks in advance!