REVO CNG is alot better in all aspects.
First of all, REVO has 1050cc Electronic Fuel Injection, while ALTO has an outdated technology engine with carburator. EFI eninge like that of REVO is more fuel efficient. The pick of REVO 1050cc is very strong, and ride is alot more comfortable.
REVO is built stronger, and conforms to EURO IV safety standards, and Adam Motors has plans to export this car to Europe and other countries in 1.5 Years.
Re-sale will not be affected, infact now is the best time to buy a new REVO, as the prices for this car are rising. REVO 800cc was 269,000 Rs. when launched and now, the price has been raised to 289,000, and who knows it will even hit 299,000 soon. That indicates that company is now well established, and recently Adam Motors has gotten financial backing from a UAE group, and you will see, alot of good products from Adam Motors in next few years. Which is a good thing for people buying REVO now, since it will create a good market presence for all of Adam Motors products in the future, and REVO's demand is continuing to increase every day.
ALTO on the other hand has alot of chances of its value and price being slashed in future, due to alot of competition now. The competition will only increase. And there are plans to eliminate Mehran and replace it will ALTO, which means, suzuki motors will put 800cc in ALTO and make it very low quality in near future and slash its prices.. to 4 lakh or so, to stay competitive in the market...
So, by all means forecasts. REVO 1050cc is the best choice, fuel economy wise, and future resale wise..