I had knitted all but the collar of this sweater last spring, but when I tried it on, it was enormous! I had rounded up to the next size since I wasn't sure which one to choose. I also lengthened the sleeves and body by an inch or two since I'm 5'10". But the sleeves bunched and it was just way too long. The proportions of the sweater didn't work well when it was too oversized, so I ripped it all out, making notes so I would choose the correct size when I started I again. In my final version, I only lengthened the body and the sleeves by about an inch.
My advice, if you're deciding between two sizes, is to stick with the smaller one. But also consider that my yarn is stretchy and might behave differently from yours.
My yarn is the Valley Yarns Haydenville bulky, in Light Grey. It's a superwash merino-acrylic blend. It's soft and nice to work with and to wear.
After I made some other projects, I started this sweater again in November. I had it mostly finished at the end of the year, and took it with me to our late Christmas gathering with the in-laws. I thought I might finish it there, while the others watched endless college football games, but I didn't complete the collar until a couple days later.
Then, as usual, I was reluctant to weave in the ends (why? I'm so close to wearing the thing! Finishing up should be the most exciting part, right?) But I finally spent a few hours finishing up some WIPs. I did this cardigan, a second sweater, and four socks (which had 5 or 6 different colors used in them). So many ends! It was pretty satisfying to finish all those things and get to wear them.