They are both good systems. Regarding weight when you factor in the
complete weight of the pedal and cleate the DA is not much heavier.
Something like 10-20 grams difference than the X1 (Speedplay Ti). The
adjustable float Speedplays some people have had problems with the
adjustment, myself included.

The dual entry of Speedplay is nice, but if you don't plan on getting
in an out all the the time it should not be the deciding factor.

I currently use X1 or X2 on all our bikes.

One thing that you may want to consider is that the Speedplay system
uses many more parts. The cleating system with it's 7 screews, 2
springs, 2 plates (shoe and outer). Last year we were on a race tour
though Europe and on of the guys with us lost a screw. He did not see
it and ended up bending the outter plate that covers the rear sping.
Needless to say we could not find one in Italy and did not have time
to go to every bike shop in Milan. He ended up buying new pedals.
Moral if you travel anywhere with these bring spare parts or use a
pedal that is more international in case of failure.

My 2 cents