how to tell which +P has moar felt recoil than non-+P ammo?

reading the lucky gunner tests, some ammo is rated +P but has lower
velocity readings than some standard ammo

the reason i'm asking is i'm looking to get the largest dia. mushroom +
penetration without too much recoil; yea, i know you need power to
make the boolit expand, but there's a fine line & i can't afford to buy
alot of boxes of $1.00 a shot fodder to find a starting point.

thanks

+p refers to the higher pressure level of the cartridge, not necessarily the  velocity.  Higher pressure should produce higher velocity, with the same bullet, but as you showed, it doesn't always work out that way.

As far as expansion and penetration, you can choose one or the other, or some where in between.

I know this doesn't help much, but there are no easy ways to judge cartridges with loads as similar as what you find in .38 and .38 +p.

You will probably have to shoot them to really discover how they act, though you can estimate if you have reliable velocities to go by.

thanks

Lucky Gunner Labs has collected some pretty good data on .38spl ammo (as well as other calibers).  Short barrel, standard pressure, +p, etc.  They have assembled a great site where you can sort by penetration, velocity, or average expansion.  Nothing is perfect but it's an interesting read.

The 158 gr LSWCHP +P has a good track record.  They called this the Metro load or FBI load.  LEOs used it short barrels.  I carry it in a 638. Its hot but manageable.