I've got two iPhone 5Ss on AT&T (64/silver and 32/space grey). I'm trying to figure out if I want to upgrade it to a 6S on my current AT&T unlimited data grandfathered plan (I'm NOT super happy with it) or if I should just jump ship with AT&T and maybe give T-Mobile a try instead. Though I'm on the "unlimited data" plan I never use much data on either phone and it seems that I rarely get a fantastic cell signal strength- almost as if AT&T is limiting my plan to lower cell tower speeds. Even in the middle of a larger city, I get like one dot or two on cell signal strength. One of the reasons I might go for an upgrade would be if it somehow made my use of my watch more enjoyable/easier/better. So, does anyone know if there is any direct benefit to using the latest iPhone in connection with the watch, or if it doesn't really matter much which generation of phone is paired to the watch?