I've only driven BMW's and own a 2010 1 series 125i coupe. I simply loved the shape and how compact it looks. If I could have afforded it I would have gone for a 135i, but in hindsight I'm glad I didn't. My previous car was a 320D which I owned since new from 2006. With the new 2 series coming I am keen on a Diesel as the 125i is very thirsty and believe me I keep within the speed limits.
Having said all of that, my neighbour has a Merc CLA and I can't count how many times I've stopped to admire it. I hear the new C series will be something to behold too, so who knows, before I put pen to paper for that 2 series, I might pop in to the Merc showroom first.
One thing though, and it's a really small thing but what I like about the BMW dealerships is that whenever my car has been in for a service, it's been the 1 hour service. Gone are the days when you drop your car at 7 am, then get dropped at work, only to ask a buddy to take you back after work to pick up your car and hope it's not too much out of his way. My car has been in 3 times for a service and each time I arrived at my appointment time and get my car back within the hour. I don't know the Merc processes that well but do they offer a similar service? That might swing it for me