Personally I prefer to only deal with digital goods and hence my preference is with Clickbank... That's because I like to offer digital bonuses (ebooks, video, audio etc) as part of promotions... Also these tend to have the highest commissions versus actual goods delivered to the door...
I think the best way to look at it is to ask yourself what are your interests and passion??? From that look at which affiliate products could fit within those interests.... and from there look at which affiliate products/platforms is best.... If your niche site is on the general subject then there is nothing stopping you from doing CJ, Clickbank, Amazon etc.... In end you need to be able to write content and the more this relates to a passion the easier it will be for you to write and promote as you already have a head start with understanding the niche, the pain points and gaps which affiliate products can fill/help others...