though it's not been my fav. topic as i have already made decision about them. anyhow
Alto is cheaper than Cultus in same 1000 cc class.
Alto has better interior than cultus. i am not mentioning quality, as both are from suzuki and needless to coment once again on quality.
without CNG cyl. alto has more luggage space than cultus.
cultus has RPM meter, better side mirrors mech, better door handles, and rear defogger, and alto doesn't have any of these.
cultus has more roomy cabin than alto.
cultus has rear independent suspension whereas alto doesn't have, actually this feature is also in cuore.
cultus has better a/c performance than alto coz it has separate fans for radiator and a/c evaporator, whereas alto has one fan and both are placed one after another.
choice is yours, i told u all points in detail.