Bowl - The professional Kitchen Aid (KA) comes with a stainless steel bowl that has a handle (yeah... we love the handle when we are transferring the contents to another dish). The smaller KA had a palm-sized "foot" that you used to lock it into the mixer... the foot was very handy to hold on to when I dumped the contents out... even though it wasn't a true handle. The Bosch came with a plastic bowl, but the ss bowl is also available. Since my husband is so great, he also purchased the ss bowl. I love ss, but unfortunately, the Bosch ss bowl does not have a handle which did make it tricky holding on to it while I was scraping out the contents. The plastic bowl already had a couple of strikes against it in my mind (because it was plastic), but after using it, I have to digress. It has a bit of a different design than the ss in that it has a lip that goes all around the top edge of the bowl. This lip makes it super easy to hang on to when transferring contents. Also, even though it is plastic, it is a nice, heavy duty, plastic that is not flimsy at all. The one weird thing that I will mention, is that the Bosch bowls have a "cone" that sticks up from the middle of them. This is where the beaters attach and they are controlled by the motor which is underneath the bowl. The cone really isn't a problem cleaning, but it is different and it takes some getting used to.
Splash guard - I purchased a splash guard for my smaller KA, but the professional one came with it. It is a clear plastic that sits on top of the bowl and has a spout that allows you to pour ingredients into the bowl while mixing. The splash guard does not attach securely to the bowl, making it very easy to dislodge. It also doesn't do that great of a job preventing splashes. In fact, when I make butter, I have to take a large tea towel and drape completely over my mixer and splash guard to keep buttermilk from spattering all over my kitchen. The Bosch motor controls the beaters from underneath rather than the top of the bowl. Because of this design, the splash guard that comes with it is actually a lid. It is clear plastic and it fastens securely on top of the bowl. There is no mess, no splatters, and best of all.... it guards against any little fingers getting ripped off and mixed into the batter.... Only by the Lord's grace have my children escaped "helping" mix without losing some fingers because of the race to be the first one to taste the cookie dough!
Multi-tasking - Because of the beaters being "exposed" on the KA, I can not really turn my back on the machine because of keeping a watchful eye on my kiddos and their fingers... In addition, if I am working with any kind of "stiff" dough, the machine will "walk", so I have to be aware of it walking off of the counter. Of course, you could prevent this by setting the mixer in the sink... With the Bosch, it does not walk, the beaters are not exposed, and I am able to get other things done around the kitchen without "babysitting" the mixer.
Beaters - The KA came with metal beaters, dough hooks, and whisks. The Bosch came with metal whisks and dough hooks. Cookie paddles are sold separately and the attachment for the paddles is metal, but the paddles themselves are plastic. My great hubby also purchased the cookie paddles.... ummmm probably because
Attachments - I can't speak much about this, as I don't have a lot of them. I have the pasta making attachments for the KA, and I love them. Bosch also has them available, but I don't have them. I have the blender attachment for the Bosch and I love it... but there could be some improvements. First, it is a clear plastic... for the money, why can't it be glass? Also, there isn't a pour spout. However, it does pour out smoothies just fine. The metal blades are quite sturdy and sharp, and the base that the blender fits in to is also a metal attachment. However, at the bottom of the blender (that has the part that fits into the metal thingy that will spin the blades) is not metal. It would seem that it should also be metal. But so far, so good. I haven't broken it yet and smoothie making with ice tends to give blenders around here a run for their money.
I have read reviews that say the the KA is better for small batches of whatever and the Bosch is better for large, however, I used the KA for large batches of cookie dough all the time and it did fine. However, I have tried the Bosch with a small batch just to see if it was true and I would have to disagree. It did just fine on a small batch. That being said, on my smaller KA, whenever I did a larger batch of cookies or bread dough, the dough would climb up the beater and wrap itself around that little springy thing that the beater attached to and it did make it a bit of a bear to clean up. I also noticed that my smaller KA would leak oil or some type of black stuff from where the beater attaches. I've read reviews where others had similar problems. I did not experience this with the larger KA.
So there you have it... my not-so-professional opinion of Bosch vs. Kitchen Aid. Which one would I recommend? Probably the Bosch. However, if you have a KA already, that doesn't mean chuck it to replace it. I have enjoyed my KA throughout the years. However, if you plan on making a lot of bread, the Bosch definitely wins... hands down. But if you don't have any kind of a mixer yet, I would encourage you to check out the Bosch. Money-wise, the professional KA and the Bosch are similar in price (unless you count a possible trip to the ER to attach a finger that got caught in the KA.... then that makes the Bosch much cheaper)!