I owned a 16' Arima for almost 10 years and now have a 16' C-dory Angler. Here's my story and comparison:
In 2003 I was in the market for a seaworthy 16 footer capable of overnighting. At the time EQ Marine was a dealer for both C-dory and Arima, and had a 16' C-dory Cruiser and a 16' Arima Sea Explorer sitting side-by-side in the lot. I always loved the look of the C-dory, but side-by-side with the Arima it was no contest, the Arima felt twice as big for the same length boat (and approximately same price) so I ordered one new from the factory. It was the largest size boat that I could fit into my garage and tow with my 6-cyl SUV...or so I thought...
On the water the Arima was great - so stable and seaworthy- we used it regularly in the San Juans and Puget Sound often in nasty water conditions and it never let us down. BUT, within the first year I had to upgrade my tow vehicle to a full size pickup and within the next two years decided to repower from the original 50 hp Honda to a 90 hp E-tec. Long story short - the Arima, while advertised as a compact, light weight boat, was not light weight at all! I loved the boat for what it was, but it ended up being in a whole different class than I originally planed - requiring much more power both on the water and on the road.
Now I here I am a couple of years after selling the Arima (and a couple of boats later), finally with a 16' C-dory. By comparison, I feel it is every bit as seaworthy as the larger Arima, yet it is much more within the size category I originally wanted - it performs beautifully with a 50 hp (cruises at 3500 rpms instead of 4900 rpm, using much less fuel), tows fine with a 4-cyl SUV, takes up less space in the garage, has a hard top that keeps us dry, and most importantly it's so cute it gets compliments everywhere it goes! Granted the Angler we bought doesn't have the sleeping berth we wanted back in 2003, but that was a conscious decision, we could have found a Cruiser model if we needed that but our boating needs have changed with time. My wife claims this is the best boat we've ever had, and I agree!
You really can't go wrong with either brand, my only point is that the Arima is a much wider and heavier boat for the same length (at least in the 16' class). But the 16' Arima Sea Explorer is no longer available from the current factory so if buying new you'd be looking at a 17' or larger.