73" tall and 200 lbs....XL fits me well and so would a large. It would depend how tight you want it really...what's your height and weight?
Slim, I am 75'' tall 185lbs with a 75'' wingspan and I have an xl spindrift and it fits very well. I have around a 34'' waist and the jacket isn't baggy around the waist as some xl's are on me. Not tight, but as far as puffy jacket fit goes I would say it's about perfect.
For reference I am 72" inches tall on the nose. About 185 - I wear a 34 guide pant and a large in all Kuiu top pieces EXCEPT the guide jacket in which I'm an XL. The arms are just too tight on the L, but I also have a long torso. The spindrift fits perfect.
And I'm sure you know this - but when you get your guide jacket make sure to try it with the spindrift underneath. You want to maintain that loft. My guide jacket with a tshirt only is a little roomy, with all the possible layers just right.
FYI- If you call in to place an order with Kuiu they are offering $40 off the Spindrift. If you just call and ask I bet they would hook you up with one. My commission is $5...send it to my PayPal..lol.