Some of digital marketing specialists says; "Bid high to get better results". Others says; "Bidding less is better"! What is the best practice & why?

It all depends upon the quality score and ad rank.If the quality score is gud like8/10 then you definitely need to bid less.For more info regarding it visit google partners and study google adwords exam.

in my point of view strategies always depend on the type of business you are in. we cannot say which1 is better practice.

The best practice is, if your cost per conversion is under control you can bid higher to get more traffic by which you can generate more lead or sales. Better Ad position gives you better CTR and good Quality score

Wow !!! a great question. 

Well I would say it depends what your objective is. If you've got a very highly structured & segmented account with proper adcopies (i.e., a highly optimized account) then there's no harm in bidding higher to get better results but if its otherwise you may end up with lot of wasted spend on your hands.