A very difficult vote. :P
Voted for TN just because it was trailing and I can't see either train being declared as 'better' than the other. :) Would have voted for KK if had been the other way round).
Have been a frequent traveler in KK for many years, and it was always special because of it's twin-Alco links and the longer route it takes (an absolute delight for any rail-fan!!). It a great train for the general public in terms of utility, and...
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an even better train for a rail fan just concerned with enjoying a long train journey on a less-frequented route. Despite receiving some backlash on being rerouted through a longer route, the train has been a blessing for the interior regions on the very neglected Mumbai-Chennai route. While the TN retained it's tag of less halts-more speed, the KK adapted better to the demands of the region and has been a vital link here.
However, I am a bit biased towards TN simply because of history, and the aura created around it by the general public, and veteran rail fans on IRFCA. Though all the 4 south giants (AP,TN,KK) had identical schedules and facilities, for a long time after their inception, TN was still considered to be on a higher level than the others ( probably due to it being the first of the 4 and may be due to Madras still being the more prominent city in the South at that time). One could tell it was the TN coming to BZA, when all the staff and even passengers waiting on the platform would go into an awestruck, almost reverential silence on the sight of a Maroon BZA WAM4 hauling Rajdhani liveried coaches pulling into BZA in the wee hours of the morning. Such a sight would leave a lasting impression on anyone.
All the lore and history set aside, there's no definitive winner in my opinion. Both trains have good schedules, and are important trains among their routes and each has something iconic associated with it for rail fans and passengers alike.