SimplePostflop - Runs as both cloud and desktop version. Supports ICM. Easy to get started.
PioSolver - Runs on desktop only. Fastest algo. Most complex functionality. Difficult to use.
GTO Range Builder - Runs in the cloud only. Collabs with SimplePostflop. I haven't used it myself.
CREV Equilibrium Solver - Not sure if in the same league but there is something from scylla coming soon, currently in beta I believe
The first 3 all produce identical output on identical input. The differences aren't in the quality of the solutions, more in the presentation / user interface and extra functionality.
Solver software is similar in impact on the games as HM+PT were back in the day. If you don't use one you are dropping behind the curve.
Shameless self-plug to intro video to SimplePostflop on IveyLeague
http://iveyleague.com/video/25-nl-6-max-zoom-part-2