Blend Tec
Bosch is a distant second.
Don't even consider KitchenAid.
Reasons? I worked for a short time for Blend Tec (then K Tec). We conducted an experiment in which we put an equal amount of "oatmeal cement" cookie dough into one of several different varieties of stand mixers, including KitchenAid, Bosch, Blend Tec, and several others. Then we set our timers for a three minute test, turned the mixers on, and watched. Within 60 seconds, the KitchenAid motor totally smoked and burned out, leaving unmixed cookie dough. Another minute later, the Bosch and several others did the same. The only mixer still "alive" at the end of the three-minute test was the Blend Tec. And, it was the only mixer that thoroughly mixed the dough.
So, we concluded that the KitchenAid was "all show and no dough." Don't get a Kitchen Aid.
Bosch is good, and much better than Kitchen Aid, but is not as sturdy as the Blend Tec and does not have anything close to as good of a bread kneading cycle as the Blend Tec.
Note: I make whole wheat bread in my Blend Tec every week.