The standard model seems to be a little less popular because of the appearance and the fact that you are a little more limited with optic options, and I think thats why it is usually priced less.
The iron sights on the tactical model arent great, the rear peep is way too small for any sort of quick acquisition, and they sit a little too low to be comfortable, but I still picked the tactical over the standard. I personally think the standard is hideous.
The optic itself is not bad quality, its a decent optic for sub-100 yard work, but less than desireable for CQB, which is primarily what (I believe) the FS2000 excels at.
I wrote a pretty in depth review of the FS, you'll find it in the "Gateway to useful threads" that is tacked at the top of the FN forum. If youre seriously considering one, I'd say its worth a read.