If you'd find the creative one more interesting and think you'd get a better mark, do that
It doesn't have to be veterinary related because anyone who does EPQ will likely come out with the same skill set:
independent working/research, motivation, time management and essay writing, which are all things you will need to use at uni. THESE are what the uni are looking at rather than what subject you've done.
for a vet related project there are sooo many things you could do it on. I did mine on the economics of bovine TB, but I guess any current topic in vet med is good. I'd say something along the lines of health of Bracycephalic breeds (google it!), pedigree dog breeding, Schmallenberg/bluetongue virus, puppy farming, lameness in dairy cattle, the ethics of animal use, zoonotic diseases etc. the list goes on forever really.
In my opinion you should pick something you like but also something that has been extensively studied and has a lot of literature on it (which is why I chose TB)- after all, you do need to write 5,000 words about it!
Also, the stuff about 'showing you can do more than science' is BS because you're applying to do a
science subject!