1520 has a faster modem than the 640XL. Band coverage depends on your models.
Isn't there only one glossy 1520? (Red)
Dual-SIM is nice.
I got my 1520 refurbished for $220. Not a single scratch or flaw except for the slightly chewed SIM port. ($220 with tax and shipping)
I owned the 1520 and the size of the phone was a little bit to big not ideal to confortably hold and use in my hand (certainly due also to the weight and the style of the phone).
It had also a 4G/LTE connection nevertheless I had issue with the reception of the phone network (no issue at all with my 1320 before) with the 640 XL the issue has been resolve. I am not sure if there any difference between the two on the LTE speed, I think this may depend of the network provider and the strength of the signal.
The Dual Sim, what a plus !!!, I don't need anymore to take with me two phone.
My 1520 was black mat.
The touch screen is good and again the issue with the 1520 has been resolve (ghost touch).
I prefer the 640 XL to my 1520 for these reason. the phone remind me a lot the 1320: Good phone (Ok not the top of the range but good), not expensive, happy with all the basic function, so *** no stress and no pressure ***