While the two movements are visually mistakable, the differences were rooted so deeply that it ended up driving the two movements apart. And while the material, lexical nature of the pieces compared are similar, the differing relationally grants Suprematist art a poetic return-to-form due to a freedom from visual grammar. This is true of suprematism as a movement, regardless of the exact artistic medium employed. But for the sake of exploring this poetry of the visual form, we are going to be comparing works of painting, sculpture, and architecture.

1. Painting

El Lissitsky - Beat the Whites with the Red Wedge
Lyubov Popova - Painterly Architectonic

At first glance, these two pieces have similar shapes, shades and apparent style. They both have a predominant red triangle, along with grayscale circles and blocks that make up a sort of backdrop. But after a moment’s considering the parts, you see that they are ordered so as to portray different meanings. 

Lissitsky’s painting shows clear orientation, directionality between the shapes, even so far as momentum and violence. The captions tell you what direction to view the painting, and give it contextual meaning. Meaning that is implied even in the shapes before you know what the captions say. Its political, and has to do with the red/whites of the Russian Civil War. 

Popova's work shares the predominant red triangle, the abstracted geometry, the striking colors. Yet they are placed on top of each other as disparate pieces. They are all stuck, shoved together, with less obvious relation. The exact relation between the objects is ambiguous, as is the angle of observation, the painting’s orientation, and other mediation. Even symbolism is escaped and subverted. And thus, more attention payed simply to the shape, the line, the layering.

2. Sculpture  
Vladimir Tatlin - Counter Relief
El Lissitzky - Proun 19d

Both Tatlins and Lissitsky's pieces present projections of depth, three dimensional form and perspective. They work with similar shapes and colors projected at similar orientations, but with entirely different intensions and application of their lexical elements. 

Counter Relief has plenty of vested meanings and intentions, despite its apparent abstraction. It maintains itself on a wall, its parts working in tandem to keep it fixed up on the wall. Its proportioned in a corner, and remains the center of attention, with a fixed angle of perspective. In light of this physicality, there’s an emphasis on functional materials, and their collective physicality, and industrialized sources.

In Proun 19d, like any piece of suprematism, one's perspective is a matter of variable orientation. Its about the use of depth and structure not distracted, by prescribed perspective, or orientation, by symbolism, and most distinctly, by physical space.

3. Architecture
Vladimir Tatlin - Monument to the Third International  
Lazar Khidekel - Floating City

Both of these pieces are speculative works of architecture, never to actually be constructed. However they were both conceived to use architectural structure, physical space and environmental integration as their means of expression. To this extent, they both have similar usage of negative space, and stark, geometric forms. However, that’s where their similarities end.  

Tatlin’s sculpture was called Monument to the 3rd international, and even from the name, there is a hint of politics that only grows stronger. The political nature of the piece is evident even in its structure and material, the tower made up of steel, glass, etc. Rising, phallic.So too did it have an incredibly detailed political intention and purpose, complete with megaphones and cameras. 

Lissitsky’s was different. It’s called a floating city, but only in name. Does this look like a city? Its not burdened with political purpose, or even by purpose at all. More interested in idea than actuality. No focus on materials or their source. Instead, Khidekel’s buildings existing as forms in nature. Not surpassing them, but incorporating them. All was organic, more interest in aesthetic than purpose.
So, what’s going on here? Three examples of Supremitist and Constructivast art with similar constituent parts. Similar lexicality. But, different relationally. Differing grammar. Whereas the Constructivist pieces tended toward constructing representation, both political and symbolic, the Suprematist pieces leaves relationally mostly up to the interpreter. A return to form, away from symbols and objectivity. And towards Poetry, if you ask Roman Jakobson. 

That’s what Jakobson’s call is. Poetry is the utterance for the purpose of expression alone, without need for the mediator of grammar. Suprematism, in contrast to Constructivism, is a return to poetry based on a subversion of visual relationally. Visual grammar. A grammar that doesn’t act as a mediator, so far as it invites multiple subjectivities.  In Suprematist art, these subjectivities are invited by a lack of clear relationality involving object priority, orientation, visual perspective, etc. “Suprematism is about Supremacy of pure artistic feeling.”