Bear in mind that +P denotes PEAK pressure up to 10 percent above SAAMI specs for that cartridge.
And +P+ (not a SAAMI term) denotes an indeterminate higher PEAK pressure.
Neither +P nor +P+ have any direct bearing on bullet energy or performance.
Easy to have a bullet and case combo that gives poor bullet performance at extremely high PEAK pressure with one powder and outstanding performance at standard PEAK pressure with a different powder.
+P and +P+ are indicators of how much stress is placed on the gun, they are NOT indicators of how hard the bullet is being pushed.
Shop your ammo by performance. Velocity, wt, expansion, accuracy, consistancy etc.
Sam