The overall look and feel of this painting is absolutely astounding. From the rich vibrant colors to the dynamic view, looks well designed and overall really well-done in my opinion.
What really stood out to me at first glance was that Rainbow Dash looks hand drawn even though the background looks watercolored, this was a risky move on your part to combine two totally different painting styles. It could've looked horrible and completely out of place or it could've complemented each other to make the paintings look astounding. And you nailed it right on the spot, not only does the background complement Rainbow Dash and vice versa, it also adds to the overall dynamic feel of the painting.
Next is the background, the background ITSELF could be a painting. From the reflections of the birds on the water to the giant waves in the sky, this background just screams dynamic. Like how the clouds complement the waves or just how much detail you put into each individual bird, just is overall amazing in itself and you did a great job trying to make the background as dynamic as possible.
Finally is Rainbow Dash herself. I never really liked very neat drawings or paintings. I always felt like it was too unrealistic to have everything neat and smooth all the time. But what you did to Rainbow Dash was absolutely amazing. From each individual feather to the color strokes in her mane makes Rainbow Dash looks very dynamic and artistic. The thing i like the most about Rainbow Dash herself (and you might not like me for this) is her posture. I have no idea why but the thing that i like the most about Rainbow Dash is just the figure she is in. But I also love the way you drew Rainbow Dash's wings. How each feather has a different shape and size, really shows how Rainbow Dash is defined in the painting. And you can't forget about the little details, I really like how you outlined rainbow dash herself and how you shadowed her from the sun really adds to the overall dynamic feel of the painting. Taking everything into consideration, the way you drew Rainbow Dash really shows how defined and different she is from the background and really shows how dynamic this painting is. Overall i really like Rainbow Dash as she bring a whole new aesthetic to the painting.
In conclusion the painting itself is very well-done, well designed, and well realized by the artist. You did a great job at making the painting as dynamic as you can, and you deserve a spot on my favourites list.
But one thing i would have liked to see was a trail coming from Rainbow Dash's wings and/or tail. It would have improved the visual aspects of your painting.