damn, this is a tough one that im have been debating since the end of 2013 (the day i bacame a brony) on 1 hand, you could (quite possibly) be ur OC in the world of ponies, living out ur day to day life as ur OC would, on the other hand u could be u but have ur very own pony in the human world .... lets take what we already kno into considuration here before i blert out my oppinion on this subject .....
now lets start with the obivious point, if we were to become our OCs, we would act, walk, talk, associate and be who we wanted our OCs to be basically (so if u kept it realistic like me, then u will be realistic, but if ur god like mary sue black and red alicorn with robo wings and kills ponies then well, thats how u would be ...... but i digress on this topic as its not the point im making atm) then we would live out our lives we have created, but if we came in contact with other ponies, like to hug them or something, it would have to be ponies close to us unless u want it to be called a filly fooler in public, or if it was to a child, a foal fidler (im sure at this point we all know about what they all mean) and risk imprisonment from the royal gods themselves....
ok now lets look at the other side of the coin, and to do this i need to reference a certain clop fic called Twi and Me by hot sauce (im not going to go in full detail as i know it will get me banned, but the information i will use is ok for this forums .....) as we already know in several fics (my little dashie in particular but not limited to) we know that the average mare or stallion would be about the size of a dog .... maybe even a puppy for the fillys and colts, but we would (or at least i would, idk about other bronies and/or pegasisters in the fandom) in time, fall in love with our pony companion, maybe like a ship kinda way, get injured, and be at our homes with our pony companion at our side, making us feel better ..... (im gonna stop there because i dont wanna get banned)
both sides have some damn good points and some damn negative ones too, for example, if i became a pony, i would lose access to the real world and be cut off from my irl friends and (this one is different depending on the person, but because i cant live without red meat in particular, its a huge problem for me) become a vegatarian, if i had a pony companion irl however, i cant take her/him on walks because all my friends would think im a weirdo, and i would lose all respect from my step-father (not that i care for it, he wants me dead anyways, but thats not up for discussion in this fandom as that is a personal matter) and that wouldnt be good for business for me, as well as making sure the pony doesnt see u eating meat and u need to let them outside to do their business (we all know what i mean here) .... hmmm after all that, i still honestly cant answer the question ..... oh i hate it when my brain is like this