The Gradient Revolution and Helsinki both have exceptionally smooth power response (something a good omni also achieves), but the design goal is radiation pattern control to reduce early room reflections, rather than omnidirectionality. In my opinion one of the primary advantages of an omni is its smooth power response, but there are other formats that do a very good job in this area - the dipole/cardioid/waveguide Gradients being among them [dealer disclaimer]. In fact, there are dipolar and bipolar speakers whose characteristics more closely approximate an omni than the Gradients' do. The Genesis Model 5 and its descendents come to mind - though not technically an omni, its presentation leans in that direction.
John Huff makes custom speakers using the German Physics DDD driver.
Long-gone Design Acoustics used to make a big quasi-omni soccer-ball-on-a-pedestal. Epicure/EPI also made quasi-omni speakers that had a midwoofer and tweeter on each vertical face of a large columnar tower.
Duke
dealer/manufacturer
John Huff makes custom speakers using the German Physics DDD driver.
Long-gone Design Acoustics used to make a big quasi-omni soccer-ball-on-a-pedestal. Epicure/EPI also made quasi-omni speakers that had a midwoofer and tweeter on each vertical face of a large columnar tower.
Duke
dealer/manufacturer