I'm 6'4" and 215lbs, 37" sleeve, considering...
I'm 6'4" and 215lbs, 37" sleeve, considering this shell for hiking, backpacking, skiing, sailing... what size would you recommend?
Although you did not provide a chest measurement, considering the measurements that you did supply, it would seem that an XL might be suitable for your intended uses. However, that might make the sleeve ride a bit on the short side as opposed to being on the longer side - depending on your preference, that could be a boon or a bane if you did decide to settle with an XL. However, the chest on an XXL is for someone with a chest measurement of 50-53 in, whereas the XL chest measurement length is 46-49 in, so I would look into measuring your chest before making a decision one way or the other.