I would consider the DA 100. The neck on the carburator is too long on the 3W engine so you would have to cut the cowling to allow the carburator to protude the cowling/fuselage, quite irretating.
If i got to choose again i would use the DA engine(i now have the 3W 106qs)
I cant think of another reason sinse the 3W 106qs is a fearly good engine. The DA is a much easier engine too install.