The bottom line is to buy what you like and not worry about resale. If you are going to keep a gun long term, resale value means little.
My first gun ( Jan of 2010 ) was a new stainless GP 4" 357. I had settled on a GP 4" and not knowing any different got the 357. The GP is now the house gun and a LCR 38 carry. Both run 38+P as firing a 357 in the house is way too loud and I want comon ammo between all guns I own.
So, knowing what I know now, a GP 38 would have fit the bill just fine.
I'm pretty sure there are some pictures of a GP 38 and 357 on the Ruger web site. I'm also pretty sure the cylinder is shorter and the forcing cone area of the barrel longer to meet the cyl. Other than that I don't see a diference in barrel strength.
Supposedly a gun built for 38 is slightly more accurate than a 38 shot from a 357 but I have no hard data. Other than that and supposedly some police depts forbiding 357 as carry opting for 38, I see no reason to make a 38 when a frame is designed to be strong enough for 357. ( The LCR 38 is aluminum framed and the 357 steel, in that case I can see a market for the 38 )