Fed reached 25 finals out of 50 times in the main draws.
Nadal reached 16 finals out 33 Grandslams.
Quite equal stat.
Fed's peak came a bit late while Nadal peak earlier. While Nadal has good stat since 2003 to date I guess Nadal will lose more from now on until he is 31 than Fed from 25 to 31 years of age. It would be interesting to look back the stat when when they are both retired.