Hi, if you are ordering online, I would suggest you buy both sizes to try on and keep the one that fits you the best.
I do that all the time, and I just return the one I do not want. I do it for peace of mind.
On your size, I know many people like to size down so they look like they're not wearing an oversized coat, but oversized is the look. It is not meant to be a fitted look, and I think some people are not used to the slouchy look so they downsize. I think people also size down as buying the "bigger" size can be a mental thing too. Ignore the sizing number; it is just a number. Always go for fit.
For Max Mara, I have found their sizing chart to be true to size for me. I am a US size 2 or 4 which is IT size 36 or 38.
For coats, while I always try on both sizes, I seem to always end up with the larger size, the 38.
The decision in choosing the size for coats is not so much your weight or height. The key to a good fit is your shoulder width as these coats are all about the shoulder.
I am 5' 2", 108lbs, but I have broad shoulders for my height. This is why sometimes I am a size 36 and others a size 38.
For Max Mara, I seem to buy the size 38, the bigger of the two.
One more thing... sizing is just a number. I can tell you are not hung up on buying the "smaller" size given your question.
Some people are hung up on buying a bigger size, and I would say this...
Ignore the numbers. If you are used to buying FR clothing sizes, they are numbered so small. UK numbers seem so big!
For me, I am a US 4, UK 6, FR 36, IT 38, NL 34. It's so crazy if you look at it. It's just a number.
So... ignore any mental anguish of a sizing number. Order them both, put on your thickest sweater, button the coat up, cross your arms back and forth and feel the pull, look at you shoulders, and then decide which you love the most. Look at the fit, and "feel" how it fits, especially when you cross your arms back and forth.
Here is the Max Mara sizing chart which I find to be accurate based on my purchases.
Hope this helps, and congrats on your soon to be new coat!
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