An MSc (extra year after you have completed your BSc) is generally considered better than the MSci in terms of PhD applications as you will do a second, more rigorous, research project.
Obviously you need to factor in any extra costs, and having to apply to institutes to get onto the course.
However I am from a biological sciences background where competition is much more intense, if I were you I'd go and speak to some academics in your department to see what they'd expect to see from strong applicants.