@ayousif00 I have similar feelings about the platforms as @craig-mulligan . They are all quite similar, there's a real convergence is going on in the platform space, IMHO.
I worked a bit more with Watson and ARTIK. ARTIK seems to be more in flux last year (things were changing around in the platform and SDK that needed some fixes in my code sometimes). They have a free tier that is not too bad, seems a bit fewer options than others, but plenty for my own data logging project that's running since the summer. Watson was pretty simple, feels like a bit more closed garden, but more services internally (most of which I haven't tried, @mccollam might know more about Watson). AWS IOT is indeed good, needs some work to set things up, but when that is done, there's a lot of AWS features to take advantage of/couple to. Seems to me, that any of them could be a good start, if you have no preference. Look in their docs/site a bit, and can follow your gut feeling, until you have more info based on your experience.