Two quick comments...

Any high drag high wing loaded plane will have a steeper glide slope with power off, i.e. deadstick. Such planes (like the Duraplane) will still deadstick just fine, just keep in mind your glide will be steeper than with lighter loaded cleaner designs. If anything, they make it to the ground quicker . I think that is what others have tried to express. With power off it feels like you are flying a brick.

As for ARFs, I got nothing against them. For anyone that wants to get in the air quick or has no interest in building, they are great. I've had a few in my day. However, there is still an advantage to building besides pure enjoyment as was indicated in this thread. I can easily build lighter and/or stronger than any ARF I've seen, and that equates to better flight performance. Not saying ARF performance is bad, it is not per se. But a well built kit plane will easily out perform any ARF I've seen. OK, I can think of one ARF that would be hard to out build, but not impossible, but I don't suggest it as a second plane.

Cheers