We study the characteristics of the low mass pp¯ enhancements near threshold in the three-body decays B-->pp¯K and B-->pp¯pi. We observe that the proton polar angle distributions in the pp¯ helicity frame in the two decays have the opposite polarity, and measure the forward-backward asymmetries as a function of the pp¯ mass for the pp¯K mode. We also search for the intermediate two-body decays, B-->p¯Delta and B-->pDelta, and set upper limits on their branching fractions. These results are obtained from a 414 fb data sample that contains 449×10BB¯ events collected near the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy ee collider.