Speaking of his role in JA, I think he really did justice to it and made an impact. The movie would have lacked something good if he weren't there. Of course he is very handsome, IMO, but can't be compared with the Greek-God-looks of Hrithik Roshan.
In any case, I think even his voice sounds so similar to Raj Babbar's and so do his expressions. But I think Sonu has a bit of cuteness to his face, which Raj Babbar lacks severely. I was disappointed (kind of) to know he isn't a Babbar. It's funny I looked at Arya Babbar's pictures today as well and realized he doesn't look anything like Raj Babbar, but Sonu looks a lot more like him. Funny how people look like others without being related to them. Reminds me of Sameer (DCH) "mere khayaal se har kisi ki soorat kisi na kisi se to milti hi hai".
Check out the similarities in their features in the photos below: