I've noticed some commercial .45 lead bullets defined as '45' and '45LC', both bullets being the same diameter and same weight- The boxes were closed, so I assume there is a difference in bullet profile? Does it matter which I use in my S&W .45 Colt?

Depends on the company...could well be the only difference is the printing on the box. So long as the bullet fits your bore and has the apropriate crimping groove, should work.

Take it by "S&W 45colt" you have a double action Mod. 25 type (or mdenern numbered version) revolver...with S&W into 1911's and the reproduction top breaks, could be something different that I assume.

To the purest there is no such thing as a 45 Long Colt, 45LC, there's 45 Colt! :D
Supposedly all the makers of 45 handguns, both revolvers and semi autos got together and determined that all 45 caliber handgun barrels should be .451.
Bullet manufacturers made the bullets .452, this works as long as you are using jacketed bullets. Lead bullets in any of the revolvers, sized .452 will lead your barrel like crazy. Why? the cylinder throats are .454 or larger.
Personally, I'm suspect of any manufacturer who mis-labels his product.
The neighborhood curmugeon
Jim