My concern with Delap is that apart from his 12 goals in 40 appearances at Ipswich, his goal record, even in the Championship, is poor, his injuries are a worry, and he looks like he lost his head at Chelsea. I wouldn't completely write him off and if he can get it together and realise even part of the hype he has high upside potential in terms of increasing value because he is English and a centre forward and we don't have many good ones of them coming through. But he could be the new Connor Wickham, Francis Jeffers etc who completely fades away and ends up in the lower leagues when his hype is fully spent.
Mateta would be a lot better. He is more ready made and can do more stuff that Chris Wood does. Delap is more like Igor Jesus.