Are "What's the Use of Feeling Blue?" by Patti LuPone as Yellow Diamond and "Open Up Your Eyes" by Emily Blunt as Tempest Shadow/Fizzlepop Berrytwist similar in any way? What about which MLP songs are similar to "It's Over(Isn't It?)" and "Love Like You"? What about which SU songs are similar to "Time To Be Awesome" or "One Small Thing"? Is "Here Comes A Thought" like "My Past Is Not Today"? Which songs from both franchises are similar to each other?

Well, I can surely see the resemblences within each of these songs, though I can't really say more songs off the top of my head that would compare between both. MLP has WAY more songs than SU does, and most of the ones from SU are more plot-focused than MLP songs are plenty of times.