I'd be torn on Benitez. He's a good coach, he'll know most of the squad already and know where we need to improve. He had submitted plans to upgrade the facilities and academy etc. However, there's always a concern about going back. You're right, he did sign some good players (Schar, Almiron, and players fit for purpose in the Championship season like Ritchie and Gayle), but he's bought some stinkers as well; Sels, Lazaar, Gamez etc. How much of that was because of budget/recruitment restrictions, I dunno?
Give him a couple of seasons then replace him with someone a little more adventurous/exciting? Maybe even offer him a DoF role?