I would say that your choice would depend on your life style. If you are an outdoors person, the .357 would make more sense(to me). If this just for nightstand duty, the .38 +P should be fine.
I pulled these figures off the Federal balistics charts. I compared bullets close to the same weight.
Hydra-shock .38 sp +P: 129 gr at M.V. of 950 f.p.s.; M.E. of 259 ft. lbs.
Hydra-shock .357 mag :125 gr , M.V. of 1440 f.p.s. ; M.E of 578 ft. lbs.
Note: These are from a 4 inch vented test bbl. and will be reduced in a snubby.
I generally keep .357s in my 2 1/2 in D.W., and have reloads handy in both loadings.
Most of my range time is with the .38s.