I like to wear a watch, so I kind of wish I could get a fitness tracker (with heart rate monitor) that doesn't have a clock on it. I sometimes wear a watch and a fitbit and that just looks stupid.
I have a (very modest) collection of watches that I enjoy wearing but I also like the data collection of a Fitbit.
The Blaze is newer than the Surge; it's basically a Surge with a color screen and the face detachable from the band (which is much better for charging, as well as making replacing the band practical) but without independent GPS (which means if you want to do run tracking without carrying a phone, the Surge still has an advantage.)
The Charge 2, IIRC, replaced the Charge about the same time as the Blaze was introduced, it's basically the next tier down from the Surge/Blaze.
(Current Blaze and former Surge and before that Flex user.)