You are right to say Tosun and Onyekuru have a similar record in the Turkish League. I think whats quite critical to point out though, is Onyekuru has a very good record in the Belgium league too, while Tosun has a good season in that league and thats about it.
The 2nd point to note is the ages of players. If you are still playing in the Turkish League at 26 it's unlikely you are going to be good enough to make the grade in a top European league. Whereas if you are 21 then you stand a good chance if you put the same sort of stats together.
The final point I'd make, is that Onyekuru's game suits the PL. He's direct and fast. You can see he would deal with the physicality of the league and many teams play now with wide attacking forwards which looks to be his strength.
Most strikers in the PL are either extremely quick, or well over 6 ft. Bosun is neither of those. I said at the time he reminded me of Jelavic & the Spanish lad who went to Spurs. Good finishers but in a more powerful league would struggle to get chances.
None of this means Onyekuru will make it here, but he has much more of a chance than Tosun ever did.
I'm always amazed at some of our fans and where they think we are really. We are a very ordinary team. I see Turkey is sandwiched between Ukraine & Holland in the leagues rankings. Imagine if we were linked with a winger playing for Ajax who was 21 scoring a goal every other game. Or the same from Kiev. People would be extremely excited about it on here. Yet when it's our own player there is a scepticism. Maybe the scepticism is right and we get too excited about new players, but there is without doubt a major disjunct.
I have no idea if Onyekuru would make it here, but I've seen enough over the last 5 years to know we can't afford to caste such players aside.