Moyes inherited a team that was fighting relegation and turned it into a team that routinely finishes in the top 6 and out performs teams who have much bigger wage bills and so presumably better players.
Martinez inherited a team who were about midtable and turned it into a team that fights relegation and only finishes above teams with smaller wage bills and so presumably worse players. And QPR.
Don't think he really had a choice in selling Valencia, N'Zogbia, Moses and losing Rodallega.
Strange that you're placing blame on him tbh. If the owners had allowed him to keep those players i could easily see them being midtable.
Moyes came in and yeah, he had to sell Rooney, but he then went and spend £30m. Then he spent £4m, then the season after that £10m, and finally £6m. It is only in the last three seasons that he's been strapped for transfer money.
Lets not pretend that Moyes didn't have cash to take the team from bottom half to top 8, because he did.
In comparison, Martinez came in and spent £6m, but lost Cattermole and Valencia. Then he spent £7m and it would seem made a mistake with Boselli. Go back though and you'll see some Boselli type purchases on Moyes' record too. Last season he spent -£2m and lost one of his best players in N'Zogbia. Most recently he's lost another two of his best players and not been given cash to replace them, but has seemingly made a good find in Kone.
Some managers will do better with limited funds than others. I'm sure there are plenty of other managers who would struggle to match Moyes' efficiency in the transfer market. But if Moyes had taken over Wigan instead of Martinez and been given -£11m net spend over three seasons i'm not convinced he'd have them finishing much higher than they do now.