Robert, it depends on what kind of photography you are primarily interested in.
If it is more studied works, where you set up and take your time, such as landscapes, casual architectural images, or dramatic wide angle still lifes ... then the SWC is a great tool to have.
You can get the Hasselblad ground glass and various finders for critical focusing if desired ... although the depth-of-field of the 38, using hyper-focal-distance focusing also makes it useable for many other applications.
On the other hand, if you tend to shoot more spontaneously like street photography, weddings/events, general travel landscapes and such... then the 40 may serve you better.
I have both, and tend to get more use from the 40mm. This is because of the type work I tend to do, and that I need the 40 when using the CFV digital back that produces a 1.5X crop factor ... as opposed to optical considerations. Optically, the 38 is more highly corrected than the 40mm, and does focus closer ... although an 8mm extension tube will remedy that on the occasion you wanted to focus the 40 really close.