GT stops for 120 minutes in various stations whereas TN stops for 62 minutes only in less stations. GT has got various 1 or 2 minute stops whereas TN has 3- 3mnt stops and 2-2 mt stops.
that is why GT takes more time than tn. running time diff is only 1 hour after deducting stops for both trains.
gt is a old train and is never cancelled - it may go on a different route but is not cancelled, whereas tn is canclled.
the...
more... choice of train is on the blogger. there are other alternatives like TN Sampark Kranti Express, Duronto (twice a week), Rajdhani, Garib Rath, Dehradun Express etc. Duronto, GR & Rajdhani take less time (28 hrs) than TN or GT. choice is absolutely yours. Comfort wise, both TN, GT are the same.