I think Rowett is a fair improvement on Marti but I don't think he's a good manager. I think he's passable, at least with the limited time he's had with a dejected and disjointed team.
Marti was sacked not just because of recent results but because our performances were shocking. Oxford awful, Wrexham awful and lucky, Cov we only played one half of football, West Brom we were appalling and got incredibly lucky, Sheffield awful, Derby we edged it but both teams mediocre.
Compare to performances under Rowett, Stoke we were the better side, Middlesborough second best but competitive, Norwich shocking, Ipswich shocking and lucky, Bristol good, QPR awful, Watford we were the better side and deserved to win, Preston again we deserved to win. Mixed bag but improvement.
There's noticeable differences on the pitch too. Fewer wasted misplaced passes in midfield (the sheer volume of wasted passes was becoming unbearable by the end of Cifuentes' reign), players don't look as gassed or lazy in the second half and can actually fight and grow into games. Still think we have set piece issues at both ends and players need to put away chances. He was brought in to manage a group of players that to be frank wasn't being managed by a clueless Cifuentes and yeah I think he's doing that. Hope it's enough but I'm not predicting anything.