If it were my choice it would be the 640.
I belt carry 99.999999% of the time, so the extra weight of steel over aluminum wouldn't be a big issue. If I knew I was going to be primarily carrying it in a pocket or ankle holster, I'd go with the 642.
For concealed carry revolvers I prefer either the enclosed hammer of the Centennials or the shrouded hammer of the Bodyguards. If I were to get a 60 I would have the hammer bobbed and converted to DAO. If I got a Bodyguard I would most likely have it converted to DAO, too, so Centennials win out since they're already DAO.
I never cared for the trigger on the LCR. Yes, it's light and smooth, but not enough "oomph" on the trigger return for my tastes. I prefer the S&W trigger return, even if it is heavier and not-as-smooth.
People have been happy with their Taurus revolvers. People have been unhappy with their Taurus revolvers. QC seems to be really hit-or-miss, with "miss" seeming more common. Customer service also seems to be a mixed bag. For these reasons, I would pass on Taurus.