Sometimes I feel like people who don't know what they are talking about just shouldn't post things on SDN.
Both masters and SMPs will improve your chances but tend to benefit those who have higher MCATs and lower GPAs (for many reasons that can be found in the post-bacc forum). Most importantly, they can show that you can do well in high level courses (which can alleviate some fears of a low GPA but not a low MCAT score).
Both will also help your chances at both DO and MD schools. A traditional masters, while more useful if you don't get into medical school, is less useful to use as a bridge into medical school. First there tends to be grade inflation in masters programs (for instance, many consider anything less than a B- a failing grade- causing everyone to get higher grades). Second they are usually not taken with the medical students and have a different bent to them. Since graduate programs don't affect your GPA, that you don't have a direct comparison to medical students makes them less useful to remediate a low GPA.
SMPs tend to be much, much more expensive (often >50K) but are worth the extra money since you have a much higher chance of getting into medical school.
But we need to know more about you to even decide if an SMP would be a resonable route, what are your stats.
