Usually the freezer wall has coils in it that you have to figure out where they are so you don't drill a hole through them. Also a collar gives you more depth for tubing and a Co2 bottle on the hump if you want it there. Also it's a lot easier to replace a collar than a freezer.
Thanks Hoss. Do you know of a way to locate the coils. We are thinking of getting the freezer as cold as possible then placing a pot of boiling water in it to see if it will show the coils.
Not to try and change your mind or anything, but why risk it? Collar is easy, cheap, and no chance of destroying a perfectly find freezer because you slipped, sneezed, or simply misjudged where the coils where. Or put some towers in the top. No coils in the cover. Don't like the idea of towers myself, but another option.
Even if you did manage to avoid all the coils, I bet it will be hard to evenly space the taps. Might look a little funny with uneven spacing. Maybe I'm just too anal.
For what its worth, I ruined a freezer by mounting my c02 manifold and I had located the cooling lines by using a small pilot hole and still hit one of the lines.
In my experience the lines are pretty close together, not enough to drill the 1 1/8" hole for the shank. Hope this helps
No worries about damaging the freezer- if you ever convert it back to a freezer, one just needs to disassemble the collar and put the original hinges back on.
It raises the level of the taps to a more user-friendly height.
It looks nice.
It allows more kegs/CO2 on the compressor hump, if applicable.
No danger of destroying coils.
cons:
It adds expense.
It requires some tools and skill to build and attach.
I didn't add a collar to my freezer simply because I built it before I was aware of homebrew forums, and didn't know better. What I did was build a box inside the freezer over the compresser step to hold the taps. I did carefully find a place to run my CO2 line in at the base of the compressor step, and added a distribution manifold for gas lines onto the tap box. Attached is a picture.