If you want MD, the best course of action would be to do either a postbacc or an SMP and get a good MCAT. The good SMPs are competitive and most entering students have ugrad GPAs between 3.2 and 3.5 (unless you've got amazing ECs or a great MCAT).
SMPs are 1 year masters programs where you take most of the same medical school courses as M1s and are graded against them.
MS in Biomedical Sciences programs vary by school, but you don't take the same courses as M1s and are not graded against them. The material is similar to the courses taken during the 1st year of med school, but it is geared more towards graduate (PhD) sciences and not clinical sciences.
In a nutshell, SMPs are better than MSBS programs. A regular master's will help very little if at all.
Since you haven't taken the MCAT yet, my advice would be to study hard for the test and take some post bacc science courses at the same time to raise your GPA. Then you can apply to SMPs or DO schools if your MCAT is high enough. You can search SDN for SMP program reviews, but generally BU/Gtown/Cincinnati/EVMS/Toledo/RFU are considered the best.
