Well that kind of depends on what sort of striker Benteke might turn into once you put him into a top team, with a little bit more experience. He scored 19 in the league last season, for a team that were relegation candidates until almost the end of the season. If he got more chances & knocked in 24-25, nobody would sniff at him.
For comparison, Lewandowski (who I think everyone considers a 'super' player) has scored. 23 & 22 goals in the last two seasons, though the more recent was somewhat impacted by injury.
Of course, Benteke might not be good enough to make that kind of improvement in his game - he might have had a purple patch this year alone. But you can't really make that call without properly watching him. Personally, I think both he & Lukaku look like excellent prospects. Is take either.