Apart from laxative effect,is sugar alcohol (erithritol) better substitute to sugar & artificial sweetener?or is there any other disadvantage to them?

Sugar: As a matter of fact, if you are diabetic or a weight watcher none is advisable. Develop a taste to consume without sugar.

Sugar alcohols: The funny thing about sugar alcohols is that they reconstitute into actual sugar once digested. So a product can be marketed as "sugar-free" if it contains sugar alcohols, but after absorption there's sugar again. It's a marketing ploy. So yes, sugar alcohols can have bad effects on your body just like sugar.