This Gradel thing really isn't relevant at all, I'm not sure why you keep bringing it up. Nobody can deny that Gradel scored more goals than Benteke last season, so with those stats all you can say is that last season he was more prolific. The stats would also show that Benteke has scored more goals over his career and has a better goals-per-game ratio, so you could argue that Benteke seems to be a better bet for goals than Gradel.
With Veretout and Westwood, the former has scored more goals and got more assists than Westwood has in one season fewer. I'd say that would make him a better bet attacking wise.