MT1500 is analog, P16, analog conventional and analog smartzone trunking.
The XTS1500 is analog/digital, P16 analog/digital 3600K smartzone trunking, or P25 9600K trunking and conventional analog/digital.
Notice the 'or' between the 2 trunking formats, P16 and P25 trunking, The XTS1500 is not dual mode digital trunking however like the XTS2500, XTS5000 and APX radios are.
By this I mean you order it as standard analog and digital conventional with the following options, #1. either full digital 9600K trunking or #2. analog/digital smartzone trunking, P16 3600 K control channel, but not both P16 and P25 trunking.
For the Motorola price the MT1500 can be flash upgraded to a XTS1500 but again you need to choose on your desired trunking format when you order the upgrade kit.
Mike