I have both the Bachmann inside frame (SRRL) and the LGB C&S with plow.
A few observations…
Both run extremely smooth and effortlessly.
Size does not appear all that much different, likely due to the LGB plow.
The LGB will stall-out on LGB R3 switches if running slow (Apparently the pick-ups are not spaced far enough apart to keep continued contact through the frog).
The LGB has an optional “adapter” between the plow and pilot raising the plow height and swing to clear 4ft curves and switch machines. Looks much better with the adapter removed.
The Bachmann has a rear truck that can be “un-locked” to allow smooth operation on smaller diameter track.
I prefer the looks of the LGB due to the plow/bear-trap stack but love the added detail of the Bachmann model. The Bachmann has an absurd looking coal load.
I love them both, and could not pick a favorite between the two. Can’t go wrong either way!
Edit: Forgot about your pulling power question…Both could pull a school bus but I never run more than a few cars with them as they just look better that way in my opinion. The LGB has a traction tire which certainly helps.