Battery circular saw are definitely NOT lighter than corded ones.

But even with that, I would still say battery. One of the few tools that I think is almost mandatory to be battery powered just for the pure convenience.

In terms of brands, that entirely depends on what is readily available in your area and what kind of deals yoou can find. If you have a cordless drill (which is one of the other mandatory cordless tools) then consider getting the same brand of circular saw since you should be able to share batteries. You are not going to go wrong with any of the brands you mentioned. Of those, I personally would probably go DeWalt. Definitely go with a brushless motor which will give you longer battery life and more power.