Winter coat for the business attire

I just made a purchase for a new black top coat to wear to work. I will give details about that below.

First, I would like to ask a few questions of the men in here what they look for in a top coat? Fit, length, pockets, lining? Wool or Cashmere... cashmere quality? Touch/Feel? Do you buy a size larger so that it fits over a suit?

Should I be surprised that so many people have on what I think are ill-fitting top coats?

I work in a business/politics environment and conservative is always the safest bet. Boston isn't the most fashion forward of cities and being too well dressed tends to suggest a certain flamboyance (nothing is wrong with that, of course).

In looking for a top coat, I've been on the search for at least a good 6 years for a 100% cashmere coat to replace my 9-year-old-almost-right-out-of-college-first-business-coat from Banana Republic. I've been looking ever since since I noticed it was wearing thin and I was using duct-tape to mend the inside pockets.

I was very picky about fit, however. I'm a little less than 5'7" and 38S in jacket size. Most coats run long, even in the short. Walking, I certainly don't like to feel the hem of the coat hitting my calf muscles. I also didn't want a coat that made me look too boxy.

I liked the Brooks Brothers $600 100% cashmere (probably less than many men on this forum paid for their coats), but it was too long. I didn't like the idea of having it tailored. JosABank has great sales, but their coats are boxy, the cashmere looks cheap, and they certainly don't fit me. Twice, I passed up the $400 100% cashmere at Saks 5th outlet. It fit perfectly, but I was making less money at the time and saving up for a wedding. This year, I was going to go back and buy it, finally.

However, I just walked out of Macy's with a $230 (on sale, including tax) Michael Kors coat. It is 70% wool, 20% nylon, and 10% cashmere. I saved some money and, in my mind, I suppose I won't mind walking in the snow to the subway with an inferior wool-cashmere blend. It's really not so bad. Not as soft as a luxurious cashmere, but really... it's not too bad to the touch.

Thoughts?

Winters can be harsh in Boston and I do walk with snowfall to the train station.  I'm really attracted to getting a cashmere coat, but not sure if their lighter weight and thin-ness would hold up to the weather. 

I think implicit in my search for a coat and in my post above... sizing varies significantly depending on the brand name/make.  I've put on 38S from different makers and definitely have found some roomier than others in the shoulders.

I could have bought this coat yesterday.  However, they only had a 38S at that Macy's.  It fit perfectly and my wife was told me to buy it, but I was only wearing a t-shirt.  I was told a closer one to work would have a 40S, so I went there today and tried it on since I wear a suit to work anyway.  Left with the 40S.