I own both of these frames, but until now I never compared them side by side. I like both frames a lot, and they are similar, but I just discovered that there is a surprisingly large difference in string pattern density that goes against what you might expect by looking at the specs on paper. Believe it or not the Midplus version is much, much more open-patterned at the center of the stringbed than the OS version, despite the fact that the midplus actually has more strings (16x20 in a 97si head) than the OS (16x19 in a 107si head). On the MP, the distance between the 8 center main strings is 86mm. On the OS, that distance is only 77mm. This is a huge difference, and it reflects in the way these two racquets play when weighted similarly. The MP is a little more lively and quite a more spin friendly, but the OS is more precise, controlled, and solid for volleys, blocked returns, and slices.