Both struggled with some success as ML hitters entering their age 26 season. Guti broke out, while Martin had injury issues. But their ML seasons prior to that look very similar. Prior to that, Martin really owned the minors in his limited exposure there: .321/.387/.505 for an .892 OPS. That's in 646 plate appearances. Martin always hit very well in the Cuban leagues as well, with a slash line of .308/.429/.457 for an .866 OPS.
In all leagues, Guti's lifetime OPS is .758. Martin's is .799.
I think there is still a lot of offensive upside to Martin. A lot more upside in total than what we gave him up for. And of course, that means elite defense and baserunning at a premium position. A 90ish OPS+ is well within possibility, having done that for two seasons prior to the injury washout of 2015. I think you take that package for CF, if you get that chance, and his WAR numbers indicate it.