Welcome to ECF, and the Zenith and the Ares are both great tanks. The Ares would make a good "beginning" RTA as it's a very easy build, without sacrificing flavor and has a pretty adjustable draw. It's one of my favorite RTAs. I have a Zenith as well and while I don't find it to be earthshattering in newness or innovation (other than a rather creative and easy to use topfill system) it's just a very nicely designed, solid MTL drop in coil tank. I can't speak to the 0.8 coil yet as I am still vaping my first coil which is a 1.6 coil. That one does have a break in period of about two tanks where the flavor is slightly muted, but after that, it really shines. Coils aren't cheap, but they do have longevity, I have tried many things to "get" my coil to die including running some storebought through it, and so far it refuses. I'm leaving it alone now, as I am curious at this point what LENGTH I will get (very lengthy, probably). I hear the 0.8 coil is a flavor monster out of the gate. Also has pretty adjustable airflow, and I find it to be surprisingly "cloudy" while not being much of a juice drinker. I don't entirely understand, but I'm happy with it and it does deliver excellent flavor, better than many MTL tanks (although not all) and the 4 ml capacity is nice.
I was happy with both my purchases, and I did order a second Ares, I like it that much,. I don't think you will go far wrong with either tank, although in my eyes, it is the Ares that really shines.
Best of luck deciding, and welcome to ECF. Hope you enjoy your stay here
Anna