Well, as a matter of fact, Sweet Sixteen is one of my three baby apple trees that has been in the ground now for 3 summers. So while I don't have a lot of experience with it, I can comment somewhat on the nature of how it grows.
Compared to my other trees, it is relatively slow growing, less than moderate vigor, and slow to produce. My 3-year old tree is less than 6 feet high. However, it did suffer puppy attack when first planted -- she uprooted it not once but twice and chewed the bark to where it was reduced to just a one-foot whip. However it did recover quickly -- just has grown slowly since then. I've also been cutting back the top by about 6-12 inches each of the first 3 winters to promote more branching. The branches all have had a great tendency of acute angles, i.e., growing more upwards than outwards, so this variety requires diligent training of the young branches towards horizontal every season if you want the tree to produce fruit as quickly as possible and at maximum capacity. I have not seen a single blossom in 3 years on my tree. Hopefully I'll get a couple apples in 2013.
A lot of my experience could have to do with the puppy attack and my pruning methods; however, I have also heard some of the same comments of low vigor and acute angles from others in various online sources so I do think my observations are at least somewhat valid.
The tree has been disease free in my 3 years with it. I had a little fireblight on a Dolgo Crab branch on a different tree, but immediately pruned it off and it has not spread anywhere else in the orchard. No disease problems with any of my 3 trees, really. (At least, not yet!?)
Following are a few of my favorite apples that I have tasted that you might want to seriously consider (as I know *I* am considering them):
Arlet, a.k.a. Swiss Gourmet -- resembles a nectarine in color, and resembles Zestar or SweeTango in flavor, crispness, juiciness, etc.
Hudson's Golden Gem -- resembles a pear in russet and flavor, not buttery but crunchy like an apple should be. I've heard it's prone to diseases.
Red Hook -- resembles black cherries in color and flavor, nutty, sweet, very soft apple that does not keep.
Sinta -- beautiful yellow apple. Better than its parent Golden Delicious. Tastes to me like a cross of GD and Cortland.
Zestar -- parent of SweeTango with very similar qualities. Sort of like a tart version of Honeycrisp.
Unfortunately at this point I have little if any idea as to how these cultivars grow or their disease resistance -- we'd have to look into that.
Quick note, as long as I'm in here typing anyway... I am going to try a lot more grafting again next spring, and I am also going to plant a few seeds from my first homegrown apple, which I know can only be a cross of Cortland and Fauxwhelp. If I can get any trees off those 9 seeds, I'll let them grow for a couple years and then graft them over to one of my existing trees so they'll fruit quicker and to get the seedlings off my hands, as I don't need a seedling tree in my small yard. That is the plan. Just for fun.
Happy apple tree planning.
--
Dave