HTC One M9 seems to be not much different from M8, this is not the fact though. M9 is more of evolution than revolution. It is more of iconic design. HTC does not prioritise the optical image stabilization has the other phone operators like Nokia LG, Samsung does.
HTC has advantage over Samsung by providing a water resistance design. This case option is very essential and could be considered by many buyers.
HTC improved rare camera to 20mega pixel with 4 mega pixel to the front. Increased capacity of battery.
Samsung Galaxy S6 has done away with removable and micro SD expansion, S6 starts rom 32-128 GB which is big enough or more users. S6 is composed of glass front cameras, rear panels with gorilla glass and metal edges. The cameras were given better low-light performance. It is fixed with faster DR4 RAM with 3GB capacity.