I'm 5' 7" with short legs and currently riding a Giant with a 53.5 cm eff top tube, 13.5 cm head tube, 73.5 seat tube angle and a 90mm stem. I'm currently looking at a Van Dessel G & T. Not sure whether to go with the Size 50 with the 52 cm eff top tube and 10 cm head tube, or the Size 52 with the 53.5 cm eff top tube and 12 cm head tube; both size Van Dessels have 75 degree seat tube angles. Any suggestions would be appreciated.

I think you will be sitting much forward with 75 degree seat tube angle. In that case I'm not sure it's a good idea going for a shorter top tube length. Personally I don't like riding bikes with different seat tube angle, that's the only thing I wouldn't change on my bikes

I believe I am similar to you in size. I ride a 52 Full Tilt. It fits me perfectly with a 90 stem.

I like to ride with a shorter crossframe then roadframe. My stem is also 1 cm shorter and bars are about 1 cm higher then roadbike.

Why they make a crossbike with a 75 seatangle is abit off a misteru to me because you should be able to lift your front more and this is easier with more weight on the rear...
If you buy one off these frames , I would take a seatpost with enough setback so you can sit at least as far back as on your roadbike..

If you follow my reasoning , I guess it would be normal to take the smaller size frame.