From my experience on 12685/12686 jerk i have noticed during CBC Rake days, in LHB jerks have been far less. Ride comfort in AC is smoother and silent, while in SL initially days sound was a little disturbing. One thing surely missing in LHB was the side-wise oscillation. Quality of interior, is much better, but then it depends on whether you are allocated a fresh rake or used second hand rake as is the case with 12685/12686 where there is lot of plumbing issues and issues with windows etc with lot of jugaad fixes.
Need to verify the current rakes (i believe some of the coaches from Pandyan/Cholan/Rockfort had been swapped into the rakes these days - observation based on return to MDU markings), when it was originally converted, it did have coaches from other zone as part of the rake, especially it had a lot of second hand one's 2-3 years old (Even had advertising in Hindi for restaurants and clinics from north).
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