I have said it before - Get the standard model. U can add an aftermarket rail and turn the gun into your own trirail. However - if U need the sight back for some reason - U can always put the stock sight back - and the gun is still useable.
With the tri-rail - U MUST have an aftermarket sight, or U cannot use the gun. No backup sights on the tri-rail either.
Like everyone said, I went with the white ring sight, but the USSS sight would also be a great choice (Nether requires any batteries to work) and you can still add a aftermarket if wanted.
I also would like to aquire a USSS sight but not at the current prices that are being sought which are 1/2 the price of entire weapon system. I could see if the USSS sight had a built in digital readout rangefinder to ask that much, but at the prices people are asking its ridiculous.