Spitfire Symphonic Motions and Evo Grid 3 both provide rhythmic solutions for composing, but there are some significant differences listed below:
Symphonic Motions is a dedicated plugin which loads directly in your DAW, whereas Evo Grid 3 is a Kontakt library, meaning that it is loaded inside of the Kontakt Plugin, and requires you to have bought a full copy of Kontakt from Native Instruments.
Symphonic Motions is has a large ensemble which is "Symphonic" in scale, whereas Evo Grid 3 has a much smaller chamber sized ensemble.
Rhythms and techniques
Symphonic Motions has some of the most commonly found rhythmic values such as 6th, 8th, 12th, and 16th notes played both discretely and smoothly across a number of techniques whereas Evo Grid 3 contains rhythmic evolutions, that evolve slowly over time, often quite dramatically.
Symphonic Motions is was recorded in AIR Lyndhurst Hall, whereas Evo Grid 3 was recorded in the smaller, and drier, AIR Edel.