I agree Agent that it's just one variable in how a frame plays. In fact that's central to my point.
The traditional manner of defining string density (eg 18x20) is clearly misleading. A simple measurement of the distance covered by the 12 central main strings, perhaps in mm, would be more informative imo.
According to conventional wisdom the PSLGT and MP 18x20 are equally "dense" string patterns while the PB10 Mid is an "open" string pattern. By that standard the PB is the odd man out. But that's not experience with these frames.
When you measure a Twelve String Distance Value (TSDV) the results make more sense relative to how these frames play. I own all three, all are strung with gut mains and smooth poly crosses at similar tensions, and I have all modded to around 12 oz and roughly 10-11 pts HL. The TSDV below dovetails far better with how they feel to me compared to the conventional open/16 and dense/18 nomencleture.
PSLGT (18x20, 95", stiffness 59)
PB10 Mid (16x19, 93", stiffness 59)
Speed MP (18x20, 100", stiffness 65)