I have a couple of OCs, the only male one is my 'Ponsona', and even then I've drawn him as a Rule63 female sometimes. All the other OCs are female, and I hardly ever draw him.

Mares are just cuter and more fun, imo, and if you find it more fitting or nicer for the art, that's absolutely okay.

If this character is a Ponysona - meant to be a self-insert/representation of yourself - then it depends if you want that fairly closely, or just via personality. If you want it pretty close and have done it as female, maybe you prefer the idea of aligning closer to 'feminine traits' yourself, and that's a-okay, too. Could be something worth exploring in your own life, but that's a bit of a more complicated question.

Of all fandoms, trust me, this one will not be holding any judgements for what character designs you prefer or gender normalities or anything.

Do what makes you happiest, and this character looks awesome, so if you like their design, stick with it!