Mauiblue, I don't know what role you intend to use a 649 for but will recount my experience for what it may be worth.
The day I picked up my 649-3 (.357 mag) I was actually looking for a lightweight J Frame to use as a back-up gun, carried primarily in a pocket or ankle holster.
I had a feeling that the -3 might be a little heavy for that role, which turned out to be the case for me. I tried carrying it for a few weeks but with summertime clothing it was just a bit too much.
Shortly after coming to this conclusion I was over to a neighbors house who is a retired MSP Trooper. We got to talking guns and back-ups so he went and got the one he used as his duty back-up for quite a few years. Lo & behold if it wasn't a 649 chambered for .38 SPL only.
When he handed it to me I immediately noticed that his seemed considerably lighter than mine, which, since I didn't have mine with me at the time, might have been just been my imagination.
Another thing I immediately noticed when he brought his 649 out was two or three of those wide type rubber bands wrapped around the middle of the grips (Magnas.) I pointed and asked "Was that your holster?" He said it was and that he usually carried it inside his waistband at about the 5 o' clock position.
I did make a point of asking him if he ever thought that his 649 was too heavy? He didn't.
Now with winter here I may pull my 649-3 out of the safe and give it another try. It will be up against some stiff competition since I've been using either a Model 36-2 or 642 as my back-up so the only way I may use it is if I feel the need for it's .357 Magnum capability.
With all that said, my 649-3 is defintely one of my favorite handguns and is one that I have no intentions of ever selling, at least anytime soon.