I can given a solid answer to the question of flash programming - No they are exactly the same.
If fact the same device in a different package has exactly the same specifications.
From experience in building prototypes, you might consider that the TSSOP is much finer pitch that the SOIC, and a careful inspection may reveal a small solder bridge between pins and or a pin not completely soldered.
Hopefully you have or have access to a microscope, like around 7x. Inspect from the side, as solder bridges can escape detection when viewed only from the top side.