i have a cultus myself these days and have used Altos extensively in the past though i never owned it and from my experience the a/c of cultus is better as compared to alto maybe due to the seperate fans for condenser and radiator. i am comparing cultus carby with alto carby. the a/c of efi cultus is excellent.
and one other thing in all the altos owned by some cousins and relatives and used by me i never heard from them or faced myself an overheat issue but yes the different mechanics insist that alto has an overheat issue. God knows best.