Personally for me the dealbreaker was NAND and 2GB storage for applications.

Sensation is still using slower SD memory hence why the benchmarkes are so bad compared to the SG2 even when both are dual core. It has very little to do with the CPU as both are equally matched. Also the reason why SG2 is a lot smoother and snappier than the Sensation.

The bootloader is not a big problem but it doenst give you the option to update in the future once HTC decides to end support. This is a big let down actually.

For Samsung its easy to flash if you wanted it and it is a nice option to have and with the jig, no issues with warranty or bad flashes