Sometimes you just have a gut instinct about a player. Some people predicted Van Dijk to be a flop in this league whilst others had a feeling he'll be a revelation. Others had the same feeling for Funes Mori.
Nothing wrong with that and it's all opinions, my opinion or feeling in my stomach is that Dembele can be a 15 a season goal scorer in this league whilst Abraham whilst a talented looking kid, will struggle in the PL against tighter defences with higher quality of defenders than the championship. Dembele absolutely shown Man City up in the CL for me he's worth the gamble. Celtic have scouted some decent players tbf to them in recent years with Van Dijk and Wanyama.