I've stayed in both of these. I think the Westin is slightly better, but the Eau Claire location is nicer if the weather is good because there are some eateries and shopping right across the street from the hotel, and there is an island park on the river next to the hotel which is nice for walking about. There is also a nice restaurant in that park that serves wild game. Try the rabbit, it's great.
You can pick up good suits in Calgary. Caddy-corner from the Westin there is a shop called Supreme Men's Wear. The suits are well made and of good value. They also introduced me to some micro-fiber dress shirts when they first came out. It's a good store with excellent service, as the owners work there.
Everything in Calgary is in close proximity, so either hotel is suitable location wise. It's a very nice city.
M8