I agree with Mr. Keenan that if you get an ultra-light or airweight, especially a titanium or scandium gun, .357 is probably not the way to go, as it would be pretty rough in the recoil department. But if you opt to go for something with longer barrel and/or heavier I still feel that, all-around, you will probably be better served with a .357 as you can shoot either of these cartridges.
I also agree with Mr Silas in that I almost exclusively get a gun that catches my eye and fits/feels right in my paw. But, I am the exact opposite, I shoot .357s almost exclusively.
Not trying to completely talk you out of the .38 though (I myself picked up a Model 10 this past Friday), especially in the situation described by Mr. Keenan. But if it is the only revolver you plan to have for awhile, and you plan on shooting it a lot...why not have the versatility of two calibers?