Both are good choices
Kidding aside; I was in that same boat. Once I started lurking on the S-W forum, I became convinced that used S&W's were perfectly alright. There are many on these boards that will not buy the newer Smiths - even though they are probably the finest newly built by any standard.
I had a friend who was selling an old 686 6". It felt too barrel heavy but the price was right - AND - once I got on these forums, I realized that I could EASILY get back what I paid for it. Once I started shooting it I concluded that, at least for now, the .357 is not my cup of tea. But man, is that thing accurate! Tight patterns at 75'! (which is extremely good for me). No prob, load it up with .38 +P and away I'm a happy camper. Another 'sort of' issue - it's too heavy for the wife in a HD situation.
The 'barrel heavy' thing bothered me anyway so I borrowed/rented a couple 4" ers and snubs. Me - I can't hit much with a snub so I settled on the 4" style. (Sidebar: then I bought a couple 'other inexpensive brands' 3" & 4". Don't get me wrong, they're nice guns & functional, but you'll be able to tell the difference in quality. You're thinking 'HD' so you want the very best right?). As noted on the other thread, and in the pic, I just got the Model 64, still have the 686 and a couple of other brands. I'll eventually sell one or two and get something else (lol - had you going there! Well, maybe the other brands).
End of story; in S&W - in a short time I ended up with a 686 AND a 64 for just a little more than that new 686 4" will cost you and a couple hundred more than a new 64 runs. You can't go wrong with good used S&W's - you'll get every penny back out of them. Also, you won't know which one you like best until you spend some time shooting it, carrying it, etc. What I ended up liking best is not what I thought I would like best before I owned them. (Edit: I ended up liking the lighter, better balanced guns more).
Here they are:
Edit: sorry for the not-very-good pic. Also the 686 now sports the Pachmayr Decelerator grips which helped me enjoy the .357 by eliminating/covering the exposed metal backstrap. The most shocking difference between these two is how different they feel (due to balance I think) given that the difference in weight is only about 8 oz.
Oh, and .38 is fine for home defense IMHO - though there will be those that tell you different.