Spend the scratch on the Tactical version IF you intend to mount a red dot and/or a suppressor, otherwise just get the standard version.
The FNX is a great bedside gun. I can't mount a suppressor to mine because I'm in Illinois, but a Trijicon red dot and a light up front and I'm happy.
If you don't want to spend the cash on a Trijicon, the FNX Tactical also comes with a Docter mounting plate, and some Docters can be had for $250ish. I have been thinking about buying a Docter and sticking it on the FNX so I can mount the Trijicon on a Glock.