I am betting even Freddie would have said Elton. Elton was a sort of prodigy & went to the Royal Academy (I think for 5 years) so he is a trained pianist.
Freddie only studied to level 4 & according to what he has said he couldn’t read music well & he downplayed his abilities on piano, although he always seemed pretty amazing to me & he could play classical as well.
He got away from playing piano as much in the live shows in the later years as he seemed to want to put his energy into performing. He used piano to write songs it seems. There are also stories about Freddie being able to hear a song once & sit down & play it, but I am not sure of the extent of that ability.
As to the emotion & energy they both put into their music, that’s a matter of taste but as to technical ability, Elton. I prefer Freddie’s music to Elton’s but that’s a different question.