The use of Cigar/Accessory outlet or hard wire is a matter of personal preference and application, but that 12V plug/receptacle is BULKY and as stated earlier can interfere physically if not checked and properly mounted ahead of time. There are some "power adapter" cords made for smaller plugs like the mini USB type (my TOM-TOM and cell phone come to mind), which is a nice tidy and SMALL plug/jack and it disconnects if pulled smartly (which may be desirable).
I chose for the TomTom the cigar/acc plug only because I wanted to be able to move 'cross several vehicles, but they do make a lighter plug/USB jack that could plug in and work so one could use your USB to device cord with good results.
If portability is not your bag, hardwiring (w/fuse in line) is best and you can control cord routing and ensure solid connections for the life of the machine.