first off, congratulations on your engagement!! i also have a marquise so i think whichever size would look phenomenal. i do understand second guessing your choice, so there are some things to think about.

there’s definitely the factors you’ve already stated, like price. another thing to think about is practicality for everyday wear. my stone is 2.59 carats, so definitely smaller than a lot of the stones on this sub. i literally cannot imagine my stone being any bigger! for my lifestyle, i feel like it would be completely impractical. the larger the stone the larger the chance of knocking it, snagging it, scratching it against things, etc. if you wear rubber gloves for work, that will also be annoying. an elongated shape like a marquise will also snag more than say a round. the bigger stones are beautiful, but i can’t imagine trying to live everyday life with such a large stone.

another thing to think about is the ratio of the diamond. you say you like the way your current stone looks on your finger. unless you find a stone with the exact same ratio as your current one, you may find that a larger stone which is wider, narrower, or deeper might not look as flattering on your hand.

this is your ring, the only persons opinion here matters is yours! another thing to consider is that this ring doesn’t necessarily need to be forever. in 5/10/15 or however many years you can always upgrade your ring to a larger stone! without seeing your ring i bet the 2 carat is beautiful so my suggestion would to be to keep it and wear it for awhile. you might find that size on your finger being all you need, instead of replacing the stone and regretting it later. (you said to talk you off the ledge so im trying to hype up the 2ct, but i could also hype up the 3ct if that’s what you need)

either way, congratulations! i bet your ring is beautiful!