well there are a bunch of different reasons to shoot on dslr vs a camcorder. first thing you gotta know is that most dslr's out there were made for pictures first and video second. camcorders obviously are meant strictly for video. because of this, camcorders are designed to record non stop without overheating like some dslr's do at long periods of time.
CAMCORDERS generally record in a much higher codec, or video "dna" so to speak. they also record at higher bit rates making them have higher quality images with more integrity to play around with the image in post and not have nearly as much quality loss. camcorders have an awesome build and yes almost all the good pro-grade ones have a handle and smooth zooms. unless you go with a sony fs series or even some others, they usually don't have interchangeable lenses so you are limited to that camera's lens and focal lengths. you can add attachments on the end of those lenses if you wanted the fisheye look however. camcorders have a CCD instead of CMOS sensor so with a camcorder, you don't have any rolling shutter or aliasing effects like dslrs
camcorders also have a smaller image sensor than dslrs making them not quite as good in low light situations and also making it hard to achieve a shallow depth of field.
DSLRs are usually cheaper than a good camcorder and have interchangeable lenses with a much larger sensor making it easy to achieve a shallow depth of field and also provides more options when it comes to lenses. This is where they can become pricier than a camcorder however. DSLRs for video have a much weaker codec and a lower bit rate, making the image a little more vulnerable in post production. there are also problems such as rolling shutter and aliasing that can make some situations tough for shooting. you can still do dolly zooms like you mentioned on a dslr but you have to have a much steadier hand to pull it off.
There are so many examples of good and bad footage from each camera online and really it comes down to your style of shooting and what is going to best benefit your shooting needs. Knowing all of the downsides of DSLRs compared to Camcorders, i chose the dslr route and have been very happy with it. I have also used several camcorders as well and they are a lot of fun to shoot with.
A 7D is a good camera but it is no different than a 60D for filming. Plus the 7D is more expensive. Also, T2i's are very similar in regards to filming as the other two because i believe they have a similar sensor.
For camcorders, I really like the Panasonic HVX200 and HPX250. both bad ass cameras but up there in price. Canon also has good camcorders in their pro series but they don't record to P2 cards like the panasonic ones do. So basically it comes down to what your style of shooting is and what kind of shots you want to be getting. hope this helps shed some light on the two