Synchronous buck converter - MOSFET selection
I know what you are going through.  I only know enough to be dangerous.

What I would do is use the TI Workbench.  I'd find a part that fits the In Out and amps.  Which part did not matter because once I'd hit the Back button, select "Compare All Part Type" and it gives a list of various design based on various parameters.

Then once in the selected design I'd look at the schematic they created.  Like yours, 12Vin 1V Out @ 1 amp.  This is the schematic :





From a glance at this screen, I can instantly see the design has 


94% efficiency
$10.23 BOM
100 khz switching Freq.
IC Tj 37.8°C
M1 Tj 41.1°C
M2 Tj 45.5°C
Vout P-P 0.012v




Then I'd play with the different "advanced options", efficiency, switching frequency and see which values changed in the new schematic. 

When it comes down to it , I have no clue why they selected a 25v and 30v, 100 Amp MOSFETS 

So I go into the BOM and click on the  part look at the datasheet for some clues. Then click "select another part" and it will let you select another part but only devices that will work with the current parameters and design.  Here you learn what the characteristics that limit their inclusion in the selection list. 

I would also run a Thermal Simulation.  It would show were all the inefficiencies were in the "Power Dissipation". 

For this design Cin 0.02 W, Cout 4.32mW, IC 0.11W, L1 0.12W, M1 0.22W

Anyhow I thought it was an interesting way to learn and thought it may help you as well.