I have some experience with the EAR, since I have a one-inch ATR with that setup. I absolutely love it. The deck was built by Mike Spitz (ATR Services) and the heads by Greg Orton (Flux Magnetics.) I couldn't be happier with the work that both of these guys did. The whole package--deck, heads and EAR electronics--were designed to work together, and boy do they ever. I am always happy when a job is on that format, it just sounds so delicious.
I have only heard the Aria electronics on playback...but since it was one-inch, and one of my own tapes, I felt I had a pretty good basis for a first impression. I thought the sound was great.
There's a guy in town with an Aria/ATR one inch, we've talked about getting them together for a comparison. But since these decks don't fit easily in your back pocket, it may be a while.
Even without that, however, I liked the Aria well enough that I'm planning to buy a set for another deck I'm outfitting (half inch and quarter inch.)
I have no experience with the Manley tape electronics.
My first exposure to the one inch format was several years back when I was mastering projects for Kavi Alexander. He brought along his Studer C37 that had been built for him by Tim de Paravicini. The machine was pretty cantankerous, but hooee! did it sound great. I decided then that I'd get one some day. I was very pleased to find that Mike Spitz was making one inch versions of the ATR and Tim de Paravicini was making an electronics package for the ATR. That was the exact combo I wanted, and I have not been disappointed.
Although I don't usually cross-post to multiple forums (fora?) but in this case I'm posting this information to the Gearslutz thread mentioned above, plus some stuff relating to that discussion that's off topic here.