An SPD can be adjusted to be as secure as you want or need it to be. The platform comment I don't understand. If you get a Shimano style then the platform is the same size or larger than a road pedal and you can get Shimano and other brand SPDs with cages to create an even larger platform. The advantage to the road shoe/pedal is that the road shoe will generally have a stiffer sole for a bit better power transfer. I have very good mountain (SPD) shoes and the stiffness is fine for me. The negative with road shoes is that they are not usually comfortable to walk in and with the protruding cleat you walk like a duck.