My Bosch 1617 router has the above-table hex key adjustment you mention. In use the router is fixed to the base when a cam lever is flipped - this tightens the base around the motor housing.
The 1617 actually has three rough depth settings. First I flip the cam lever to allow the router motor to move, then I push another lever that allows me to move the motor between the three depth settings - each is 1/2" difference. When I release that lever locks. Then I use the fine adjustment screw (the same one that the above-table hex key rotates) to do the fine depth setting. Then I lock it all down by flipping the cam lever.
Both the cam lever and the rough depth settings are managed under the table. Only the fine depth adjustment is done above the table.
To exchange bits I need to remove the motor from the base - its really pretty easy to do: Flip the cam lever to loosen it, press the spring-loaded rough depth lever, twist and pull the motor out. The twisting seems to be Bosch's way to prevent the motor from falling out in an out-of-control way.
The manual is available at no cost at boschtools.com .
You're correct about the Bosch, and the Craftsman is essentially the same router, in the fixed base version. The only differences are in the plunge bases.
The Porter Cable, though, has an extra hole in the base where you can unlock and lock the latch, along with the hole for above the table adjustment. Its the only one I know that can do this, and they probably have a patent on this style latch-lock. The only other way would be to buy a good router lift that has a built in lock.
I started to buy the Porter cable, until I read the reviews on the Bosch and similar Craftsman routers. I bought the Craftsman because I could get a better price, and I have no complaints with mine at all.
Now, bit changing on the Craftsman can be a bear. When you raise the router all the way up, while in the table, you can hardly reach the spindle lock button. I ended up buying a set of bit extensions, that came with the wrenches, from MCLS over it.