both are nice cars if you opt for santro make sure its the executive so u get power windows , centeral locking , hi end sound system , good seats , power steering. Now another point to note is that there is availability of parts and i hear roumers of dewan getting back in action as some of there new santro modelsa have begun to produce and sell.so resale wont be much of a problem .
As for the deut let me tell you that it is the charade of the late 90s and early 200s. without a doubt if you want class , style , performance and kick *** driving pleasure in a budget , this is the best car. You will have to forget resale.Part will be difficult to find as these are reconditioned or used cars that came in when times were good. Lastly i must mention do not let any tom dick n harry mechanic touch it or else it will be ruined.
if your looking for a daily runner get a santro else go for the duet. i dont remmber but there is a specail racing version with turbo its got air bags , bucket seats , extended bumpers and alot more worth the money try to get that one.
rgds