You can check out the Marshall Sannow stats at Handloads.Com - Stopping Power. Despite what the detractors say of MS data it gives the best comparative data for types of bullets used by police departments currently and in the past.

You will see that the flat point of the 158gr SWC in the .38 spl +P give nor significant advantage over the 158gr LRN in standard velocity. Hollow points have given better performance.

Flat point solids be they SWC or WC won't give you any better SD performance but they're not something anyone wants to get shot with and like any bullet work fine with the right bullet placement.