For many Architects SU is the quickest, cheapest and smoothest move into 3D.
Simple tools to learn, the required level of functionality (ie dynamic snapping, distance, angle, radius input, etc) and intuitive. Hides away the mechanics and just provides the interface. A very successful approach.
It’s helped from an architectural POV by the ability to import DXF/dwg’s as a base to go from.
3D Max et al are expensive, initially overly complex and not so intuitive as SU. But you probably know all this already.
So learn both SU & Blender, decide for yourself which aspects of both software to concentrate on to deliver the goods. As you delve deeper you’ll discover the benefits and downfalls where and/or if they exist.
With regard to rendering benefits in blender, blender won’t deliver photorealism, if that is a requirement. VRay will and is available for SU as well as blender, there was talk of a exporter for Lux Renderer as well, but SU as you know has a render style of it’s own and for many purposes is all that is needed.
If you are looking for photorealism ‘ArchiViz’ then you will struggle with Blender without VRay or possibly Yafaray. Lux as a unbiased render engine is too damn slow to do anything in way of animation or decent quality images in a workable time frame, production not hobby time frame that is.
Blender will allow you decent animation abilities combined with decent modeling abilities, as suggested maybe model initially in SU and animate in Blender.