We know that 2016 Nexus phones will be made by HTC and they are nick named as Sailfish and Marlin. Those names are from Google side and internally for HTC these devices are named as HTC S1 and HTC M1.
The HTC M1 is expected to come up with larger 5.5 inch display with 2560 x 1440 pixels Quad HD resolution. It will be powered with Qualcomm Snapdragon 820 SoC and gets 4 Gigs of RAM, 12 MP + 8 mega pixel combo.
The HTC S1 will be shorter in size. Today's leak by Evleaks points out at leaked build.prop file and according to it, the HTC S1 will have 5.2 inch full HD display instead Quad HD as that was found on HTC M1.
Furthermore it will be powered with Qualcomm Snapdragon 820 processor with other specs remains same as that of HTC M1.
Checkout complete HTC S1 specifications over here -