I am relating to the stock pedals come with the bikes,what makes one better than the others?How do i even make any comparison?

Stock pedals are on the bike so you can ride it away from the shop. Unless you are buying a better quality bike that may have a clipless pedal fitted- they are always platform pedals supplied and the quality is not that high. If you do want a platform pedal for your normal use then look for a pedal that has bearings fitted and an adjustment nut that means that you can not only adjust any play that comes in- you can regrease the bearings or even replace the bearings. This type of pedal is more robust and mostly made of metal with a large platform instead of being made from resin.

You really don't.

Stock pedals are meant for getting the bike out the door. They pretty much assume you are going to replace them with what works for you. A few higher end bike do not come with any pedals, and the LBS you are buying the bike from would be happy to put any pedals they have in stock on the bike for you. Probably at a hefty discount (read almost cost) since you are buying the bike.

Most riders tend to go clipless, or at least clipped in pedals very quickly since the ride is much better as compared to platforms. Hard to really spin with platforms.

So bottom line answer. The cheap platforms that come with the bike are trash. Get something on there that is better suited to the job ASAP.

Many of the plastic pedals that come stock on less expensive bikes are pretty poor. Many reports on BF of their cracking after minimal use.

Higher end bikes frequently do not even come with pedals as the manufacturers figure experienced riders have their own preferences in pedals and will ditch anything provided as original equipment in order to fit their preferred clipless pedal type.