Well this is always a controversial issue.
Dynas do have a reputation of being tough to tune. The problem is, many drummers have tuning issues (trying to be polite here) with an 8 or 10 lug standard snare drum. They like to crank the heads and choke the wires. Try that on a dyna and it will not work for you.
I currently own a couple of Cleveland era wood dynas and 4-5 COB dynas from a b&b paper tag version to a 6.5" 7 liner (the latest version I own). I do know how to tune them as I have been playing them since 1966.
I have two dynas that I actually like to play - an English built dyna and a 7 line 6.5x14. The rest don't do it for MY ear behind a kit. I have always considered them fine orchestral snare drums, but I prefer the sound and feel of an 8 lug Powertone (or Tower) over a dyna. Just part my my overall fondness for 8 lug snares over 10 lug versions.
Everyone's ear is different.